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d20b4aa3005bbe8602412746b3658946 | 33.703 | 4.2 General Assumptions
| In the present document, PQC is referred to as cryptographic algorithms that are deemed to be secure against attacks from both classical and quantum computing.
All traditional public key cryptographic algorithms used in 3GPP systems need to be migrated to PQC algorithms. If suitable PQC options are not available, then an alternative path needs to be provided and justified, e.g., deprecation, mitigation, and re-architecting.
The PQC options are to be drawn from well-studied standardised primitives and protocols.
Both hybrid and standalone KEM are in the scope of this study. Standalone and hybrid signatures are also in the scope of this study.
Editor’s Note: Further general assumptions are FFS.
5 Principles and attributes of PQC to use in 3GPP procedures
Editor’s Note: This clause contains impact of using hybrid and standalone PQC algorithms in 3GPP procedures, impact to 3GPP procedures due to larger length of PQC key, signature, and message compared to the length of those in traditional cryptography, security levels (I-V) required to align with existing 3GPP procedures level of assurance, suitability of classes of post-quantum signature algorithms (e.g., lattice-based, hash-based) to 3GPP procedures.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 5.1 PQC security level
| The NIST use the concept of security levels/security strength categories to group algorithms, keys, and protocols related to PQC [37]. Security is defined as a function of resources comparable to or greater than those required to break AES and SHA2/SHA3 algorithms, i.e., key search on block cipher for AES and collision search on a 256-bit hash function for SHA2/SHA3. The security strength is broadly grouped into the following 5 levels [8] and to each of the PQ security levels, the corresponding traditional and post-quantum algorithm can be mapped:
Level 1: At least as hard as breaking AES-128 (key search on block cipher) , PQC-Algorithm: ML-KEM-512 [21], FN-DSA-512 [36], SLH-DSA-SHA2/SHAKE-128f/s [23]
Level 2: At least as hard as breaking SHA-256/SHA3-256 (collision search on a 256-bit hash function), PQC-Algorithm: ML-DSA-44 [22]
Level 3: At least as hard as breaking AES-192 (key search on block cipher), PQC-Algorithm: ML-KEM-768 [21], ML-DSA-65 [22], SLH-DSA-SHA2/SHAKE-192f/s [23]
Level 4: At least as hard as breaking SHA-384/SHA3-384 (collision search on a 384-bit hash function), PQC-Algorithm: No algorithm tested at this level
Level 5: At least as hard as breaking AES-256 (key search on block cipher), PQC-Algorithm: ML-KEM-1024 [21], FN-DSA-1024 [36], ML-DSA-87 [22], SLH-DSA-SHA2/SHAKE-256f/s [23]
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 5.2 Hybrid and standalone schemes
| Post-Quantum Traditional (PQT) hybrid scheme as defined in RFC 9794 [7] is a multi-algorithm scheme where at least one component algorithm is a post-quantum algorithm and at least one is a traditional algorithm. Both the PQT hybrid scheme and the standalone PQC scheme are considered in the present document.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 5.3 Cryptographic agility
| Cryptographic agility [40, 41] refers to the capabilities needed to replace and adapt cryptographic algorithms while preserving security and ongoing operations. The 3GPP systems need to consider cryptographic agility.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 5.4 PQC algorithm types and cryptographic diversity
| PQC algorithms can be categorized based on different mathematical foundations. The following are a few typical types of PQC algorithms [38, 5]: Lattice-based cryptography, Hash-based cryptography, Multivariate cryptography, Code-based cryptography, and Isogeny-based cryptography.
NOTE: The types for NIST selected algorithms are as follows: ML-KEM for key encapsulation, and ML-DSA and FN-DSA for digital signature are all Lattice-based algorithms; SLH-DSA for digital signature is a Hash-based algorithm; and HQC-KEM for key encapsulation is a Code-based algorithm.
Cryptographic diversity is the practice of having different types of PQC algorithms available. This provides resilience against future attacks in case that a weakness or vulnerability is discovered in one type of algorithm, when other types of algorithms will remain unaffected. For example, NIST has chosen SLH-DSA as a backup algorithm for ML-DSA and HQC algorithm as a backup for ML-KEM [39]. A key enabler for this is cryptographic agility so that if an algorithm is broken it can be removed and replaced with an alternative without undue disruption.
6 Protocols expected to be updated for PQC by other SDOs
Editor’s Note: This clause contains the expected timeline for when security protocols defined by other SDOs will include PQC algorithms and be available for inclusion into 3GPP procedures. The timeline includes the availability of stable protocols.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.1 General
|
According to the inventory in TR 33.938 [2], many security protocols and algorithms used in 3GPP (e.g. (D)TLS, IKEv2, JWE, JWS, etc.) are specified in other standard organizations (e.g. IETF). They are expected to be updated using PQC in the corresponding organizations.
In this clause, the progress of the post-quantum migration of these protocols are reported. Mature specifications developed by related SDOs will be given priority consideration. In addition, whether the relevant solutions can be directly applied to specific 3GPP scenarios will be evaluated.
The present document discusses several IETF documents that are at different levels of maturity in the overall IETF standardization process [42], and categorizes them as follows:
• IETF Individual Draft: A document that has been submitted to IETF and has not been adopted by one of the working groups in IETF. On the IETF Datatracker website, such documents have type “Active Internet-Draft (individual)”.
• IETF WG Draft: A document that has been reviewed and adopted by one of the working groups in IETF. On the IETF Datatracker website, such documents have type “Active Internet-Draft (xyz WG)”, where xyz is the name of the working group that adopted the document, e.g., tls.
• IETF RFC: A document that has gone through the whole IETF standardization process.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.2 COSE
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.2.1 General
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.2.2 Current Work in IETF
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.2.2.1 IETF RFCs
| No RFCs for the usage of PQC algorithms in COSE are published yet.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.2.2.2 IETF Adopted Drafts
| The IETF is developing support for PQC algorithms in COSE. The following drafts are relevant:
- IETF Draft draft-ietf-jose-pqc-kem-03, "Post-Quantum Key Encapsulation Mechanisms (PQ KEMs) for JOSE and COSE" [67], describes the conventions for using Post-Quantum Key Encapsulation Mechanisms (PQ-KEMs) within JOSE and COSE.
- IETF Draft draft-ietf-cose-dilithium-08, "ML-DSA for JOSE and COSE" [68], describes JSON Object Signing and Encryption (JOSE) and CBOR Object Signing and Encryption (COSE) serializations for Module-Lattice-Based Digital Signature Standard (ML-DSA).
- IETF Draft draft-ietf-cose-sphincs-plus-05: "SLH-DSA for JOSE and COSE" [69], describes JOSE and COSE serializations for SLH-DSA.
- IETF Draft draft-ietf-cose-falcon-01, "JOSE and COSE Encoding for Falcon" [70], describes JSON and CBOR serializations.
- IETF Draft draft-ietf-cose-hpke-16, "Use of Hybrid Public-Key Encryption (HPKE) with CBOR Object Signing and Encryption (COSE)" [72] defines a Hybrid Public Key Encryption (HPKE) for use with JOSE utilizing an asymmetric Key Encapsulation Mechanism (KEM), a Key Derivation Function (KDF), and an Authenticated Encryption with Associated Data (AEAD) algorithm.
However, no IETF work on hybrid signature schemes for COSE has been adopted.
6.2.3 3GPP Considerations
Editor’s Note: This clause does not include any conclusions.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3 IKEv2
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.1 General
| IKEv2 specified in IETF RFC 7296 [80] provides mutual authentication and establishes Security Associations (SA) for IPsec tunnels. The IKEv2 is also used by MOBIKE specified in IETF RFC 4555 [81].
The IETF IPSECME group has introduced multiple RFCs and Drafts to enable a smooth PQC transition for the Internet Key Exchange Protocol Version 2 (IKEv2) protocol. They cover both key exchange and authentication.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.2 Current Work in IETF
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.2.1 IETF RFCs
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.2.1.1 Key Exchange
| KEM-based Key Exchange
• IETF RFC 9242 [43] introduces a new exchange, called "Intermediate Exchange" for IKEv2 to avoid IP fragmentation of large IKE messages and enable transferring large amounts of data during Security Association (SA) establishment expected for some PQC key exchanges.
• IETF RFC 9370 [44] describes a method to perform multiple successive key exchanges in IKEv2. It allows integration of PQC in IKEv2 and the negotiation of one or more PQC algorithms, in addition to the existing (EC)DH key exchange data that provides backward compatibility.
• IETF RFC 7383, "Internet Key Exchange Protocol Version 2 (IKEv2) Message Fragmentation" [49] describes a way to avoid IP fragmentation of large Internet Key Exchange Protocol version 2 (IKEv2) messages, which is necessary when using ML-KEM-1024, ML-DSA, or SLH-DSA.
PSK-based Key Exchange
- IETF RFC 8784 [47] describes an extension of IKEv2 resistant to quantum computers using pre-shared keys.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.2.1.2 Authentication and Signature
| - IETF RFC 9593 [46] defines a mechanism that allows implementations of IKEv2 to indicate the list of supported authentication methods to their peers while establishing IKEv2 SAs. This mechanism improves interoperability when IKEv2 partners are configured with multiple credentials of different types (for example, ECC-based certificate and PQC-based certificate) for authenticating each other.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.2.2 IETF Adopted Drafts
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.2.2.1 Key Exchange
| KEM-based Key Exchange
• IETF Draft draft-ietf-ipsecme-ikev2-mlkem-03, "Post-quantum Hybrid Key Exchange with ML-KEM in the Internet Key Exchange Protocol Version 2 (IKEv2)" [45] proposes to use the ML-KEM [21] as an additional key exchange in IKEv2 along with traditional key exchanges.
• IETF Draft draft-ietf-ipsecme-ikev2-pqc-auth-04, "Signature Authentication in the Internet Key Exchange Version 2 (IKEv2) using PQC" [69], specifies a generic mechanism for integrating post-quantum cryptographic (PQC) digital signature algorithms into the IKEv2 protocol.
PSK-based Key Exchange
- IETF Draft draft-ietf-ipsecme-ikev2-qr-alt-10, "Mixing Preshared Keys in the IKE_INTERMEDIATE and in the CREATE_CHILD_SA Exchanges of IKEv2 for Post-quantum Security" [78] defines an alternative way to provide protection against quantum computers, which is similar to the solution defined in RFC 8784 [47], but also protects the initial IKEv2 SA.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.3.2.2.2 Authentication and Signatures
| - IETF Draft draft-ietf-ipsecme-ikev2-pqc-auth-04, "Signature Authentication in the Internet Key Exchange Version 2 (IKEv2) using PQC" [48] outlines how Module-Lattice-Based Digital Signatures (ML-DSA) [22] and Stateless Hash-Based Digital Signatures (SLH-DSA) [23], can be employed as authentication methods within the IKEv2.
6.3.3 3GPP Considerations
Editor’s Note: This clause does not include any conclusions.
6.4 JOSE
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.4.1 General
| The IETF JOSE Working Group has specified the JSON Web Signatures (JWS) [83] and JSON Web Encryption (JWE) [84] that are being used in OAuth 2.0 and other procedures in 3GPP systems. For PQC migration, a few Working Group Adopted Drafts are being developed, as described below.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.4.2 Current Work in IETF
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.4.2.1 IETF RFCs
| No RFCs for the usage of PQC algorithms in JWE or JWS are published yet.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.4.2.2 IETF Adopted Drafts
| The IETF is developing support for PQC algorithms in JOSE. The following drafts are relevant:
- IETF Draft draft-ietf-jose-pqc-kem-03, "Post-Quantum Key Encapsulation Mechanisms (PQ KEMs) for JOSE and COSE" [67], describes the conventions for using Post-Quantum Key Encapsulation Mechanisms (PQ-KEMs) within JOSE and COSE.
- IETF Draft draft-ietf-cose-dilithium-08, "ML-DSA for JOSE and COSE" [68], describes JSON Object Signing and Encryption (JOSE) and CBOR Object Signing and Encryption (COSE) serializations for Module-Lattice-Based Digital Signature Standard (ML-DSA).
- IETF Draft draft-ietf-cose-sphincs-plus-05: "SLH-DSA for JOSE and COSE" [69], describes JOSE and COSE serializations for SLH-DSA.
- IETF Draft draft-ietf-cose-falcon-01, "JOSE and COSE Encoding for Falcon" [70], describes JSON and CBOR serializations.
- IETF Draft draft-ietf-jose-hpke-encrypt-12, "Use of Hybrid Public Key Encryption (HPKE) with JSON Object Signing and Encryption (JOSE)" [71] defines a Hybrid Public Key Encryption (HPKE) for use with JOSE utilizing an asymmetric Key Encapsulation Mechanism (KEM), a Key Derivation Function (KDF), and an Authenticated Encryption with Associated Data (AEAD) algorithm.
However, no IETF work on hybrid signature schemes for JOSE has been adopted.
6.4.3 3GPP Considerations
Editor’s Note: This clause does not include any conclusions.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.5 PKI certificate
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.5.1 General
| The Internet X.509 (PKIX) Certificate is being used in 3GPP PKI systems [82] and the OCSP protocol listed in the TR 33.938 [2]. The IETF LAMPS Working Group has introduced multiple Drafts to enable a smooth transition to PQC in PKIX to provide quantum-resistant security for PKIX.
6.5.2 Current Work in IETF
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.5.2.1 IETF RFCs
| • IETF RFC 9802 [51] has specified algorithm identifiers and ASN.1 encoding format for several stateful Hash-Based Signature (HBS) schemes: Hierarchical Signature System (HSS), eXtended Merkle Signature Scheme (XMSS), and a multi-tree variant of XMSS, XMSS^MT. These schemes are applicable to the Internet X.509 Public Key Infrastructure (PKI) when digital signatures are used to sign certificates and certificate revocation lists (CRLs).
- IETF RFC 9763 [50] defines a method for requesting and issuing two X.509 end-entity certificates for the same entity, in order to perform two authentications using the two certificates where each certificate corresponds to a distinct digital signature.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.5.2.2 IETF Adopted Drafts
| • IETF Draft draft-ietf-lamps-kyber-certificates-11 "Internet X.509 Public Key Infrastructure - Algorithm Identifiers for the Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM)" [52] specifies the conventions for using the ML-KEM [21] in X.509 Public Key Infrastructure.
• IETF Draft draft-ietf-lamps-x509-slhdsa-09, "Internet X.509 Public Key Infrastructure: Algorithm Identifiers for SLH-DSA" [53] specifies to the conventions for using the SLH-DSA [23] in X.509 Public Key Infrastructure.
• IETF Draft draft-ietf-lamps-dilithium-certificates-13, "Internet X.509 Public Key Infrastructure - Algorithm Identifiers for the Module-Lattice-Based Digital Signature Algorithm (ML-DSA)" [54] specifies the conventions for using the ML-DSA [22] in X.509 Public Key Infrastructure.
• IETF Draft draft-ietf-lamps-pq-composite-kem-08 "Composite ML-KEM for use in X.509 Public Key Infrastructure" [55] defines a specific instantiation of the PQT Hybrid paradigm called "composite" where multiple cryptographic algorithms (i.e. ML-KEM [21] in hybrid with traditional algorithms RSA-OAEP, ECDH, X25519, and X448) are combined to form a single key encapsulation mechanism (KEM) presenting a single public key and ciphertext such that it can be treated as a single atomic algorithm at the protocol level.
- IETF Draft draft-ietf-lamps-certdiscovery-01, "A Mechanism for X.509 Certificate Discovery" [56] specifies a method to discover a secondary X.509 certificate associated with an X.509 certificate to enable efficient multi-certificate handling in protocols.
6.5.3 3GPP Considerations
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.6 TLS 1.2
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.6.1 General
| The TLS 1.2 handshake in IETF RFC 5246 [57] is used in TLS 1.2, DTLS 1.2, EAP-TLS 1.2, EAP-TTLS, and OAuth 2.0. The DTLS handshake is also applied in DTLS over SCTP and can be used in DTLS-SRTP.
The 3GPP TLS profile is defined in clause 6.2 of 3GPP TS 33.210 [59]. Since Release 15, TLS 1.3 has been mandatory for all 3GPP core network nodes, and from Release 16 onward, it is mandatory for all nodes. Because TLS always negotiates the highest mutually supported version, any use of TLS 1.2 in a 3GPP system from Rel-16 onward implies that at least one node is non-compliant with 3GPP specifications.
While a fully updated TLS 1.2 implementation could theoretically provide strong security against classical adversaries in scenarios where identity protection is not required, in practice, TLS 1.2 is only negotiated by outdated implementations. These often suffer from one or more known vulnerabilities.
Therefore, TLS 1.2 is expected to already have been fully phased out in 5G systems.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.6.2 Current Work in IETF
| TLS 1.2 has been obsoleted since 2018, as superseded by TLS 1.3 in IETF RFC 8446 [58]. The IETF will no longer approve any additions or updates to TLS 1.2, including PQC support (IETF draft-ietf-tls-tls12-frozen-08 [60]).
6.6.3 3GPP Considerations
Since TLS 1.2 will not be updated any further, 3GPP will consider phasing out the use of TLS 1.2.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.7 TLS 1.3
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.7.1 General
| The TLS 1.3 handshake protocol as defined in clause 4 of IETF RFC 8446 [58] is used in TLS 1.3, EAP-TLS 1.3, EAP-TTLS 1.3, OAuth 2.0, DTLS 1.3, and QUIC, and it can also be used in DTLS-SRTP. Since Release 15, TLS 1.3 has been mandatory to implement for the core network (cf. Annex E in TS 33.310 v15.0.0), and starting in Release 16, it has been mandatory to implement also for the ME (cf. Annex E in TS 33.310 v16.0.0).
IETF is in general recommending hybridization of KEMs and the hybrid KEM X25519MLKEM768 [65] has already received widespread implementation support and is the default in OpenSSL. It has been reported [25] that over 40% of all HTTPS client requests now use X25519MLKEM768. Standalone ML-KEM [64], ML-DSA [66] have seen more limited implementation but are supported in OpenSSL 3.5 LTS.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.7.2 Current Work in IETF
| The IETF has prioritized post-quantum migration in TLS as follows [61]:
• Now (Hybrid + Pure ML-KEM)
• Later (signatures)
• Much later (dual certificates/composite signatures)
The IETF TLS Working Group has planned not to adopt work on hybrid signatures until "much later" [61].
The IETF TLS Working Group has introduced multiple drafts to enable a smooth transition to PQC in TLS 1.3. These proposals address both key exchange and authentication. These mechanisms collectively aim to maintain interoperability, minimize latency, and provide quantum-resistant security during and after the PQC transition.
In an LS to GSMA [62], the IETF TLS Working Group stated that they believe the IETF Adopted Draft "Post-quantum hybrid ECDHE-MLKEM Key Agreement for TLSv1.3" [65] is stable enough to be used as normative reference, and that referencing an adopted draft normatively is a practice that other organizations follow as well.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.7.2.1 IETF RFCs
| No RFCs for the usage of PQC algorithms in TLS 1.3 are published yet.
Editor's Note: several of the adopted drafts are in the final stages and may be published before this document is finalised.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 6.7.2.2 IETF Adopted Drafts
| - draft-ietf-tls-hybrid-design-16, "Hybrid key exchange in TLS 1.3" [63], specifies combining multiple key exchange algorithms (e.g., classical ECDHE with a PQ KEM) so that session security holds if at least one component remains secure.
- draft-ietf-tls-mlkem-04, "ML-KEM Post-Quantum Key Agreement for TLS 1.3" [64], proposes to use the NIST specified ML-KEM [21] in TLS 1.3.
- draft-ietf-tls-mldsa-00, "Use of ML-DSA in TLS 1.3" [66], proposes to use the NIST specified ML-DSA [22] in TLS 1.3.
- draft-ietf-tls-ecdhe-mlkem-00, "Post-quantum hybrid ECDHE-MLKEM Key Agreement for TLSv1.3" [65], defines three hybrid key agreements for TLS 1.3: X25519MLKEM768, SecP256r1MLKEM768, and SecP384r1MLKEM1024.
6.7.3 3GPP Considerations
Editor’s Note: This clause does not include any conclusions.
6.8 3GPP Considerations
All the RFCs and adopted drafts mentioned in clauses 6.2, 6.3, 6.4, 6.5, and 6.7 are stable and ready for use in 3GPP systems, except the following two adopted drafts:
• IETF Draft draft-ietf-jose-pqc-kem-03, "Post-Quantum Key Encapsulation Mechanisms (PQ KEMs) for JOSE and COSE" [67]
• IETF Draft draft-ietf-lamps-certdiscovery-01, "A Mechanism for X.509 Certificate Discovery" [56]
3GPP will consider the lifecycle management of long-lived PKIs, especially the lifespan of certificates.
3GPP will consider choosing at least two suitable standardized algorithms, if available, for the same purpose (e.g., key exchange and authentication) with different constructions so that cryptanalytic breakthroughs against one algorithm does not directly apply against the other algorithm(s).
Editor’s Note: Further 3GPP considerations are FFS.
Editor’s Note: This clause does not include any conclusions.
7 Protocols expected to be updated for PQC by 3GPP
Editor’s Note: This clause contains identification of the protocols with asymmetric cryptography listed in TR 33.938 that are not expected to be updated by other SDOs in a near future to use PQC, e.g., MIKEY-SAKKE and SUCI calculation, security threats and alternative solutions for the 3GPP procedures if they are not updated to use PQC.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.1 Threats
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.1.1 General
| Most of security protocols used in 3GPP systems are specified in other standards development organizations (SDOs). In case that these protocols are not updated to use PQC in other SDOs, the 3GPP system may be vulnerable to attacks based on quantum computation. The clauses 7.1.2, 7.1.3, and 7.2 contain all of these protocols identified and potential solutions to address the issues.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.1.2 SUCI calculation
| Editor’s Note: If only SUCI calculation is considered, this subclause may be removed. If other protocol, e.g. MIKEY-SAKKE is studied, this subclause is used for each of such protocol identified.
As per TS 33.501 [4] and Table 4.3.2-1 of 3GPP Cryptographic inventory 3GPP TR 33.938 [2], the SUCI calculation is done based on ECIES scheme. The ECIES is specified in the SECG version 2 [9] and [10].
Since ECIES will not be updated by SECG with PQC algorithms, 3GPP should study alternative solutions for SUCI calculation due to post-quantum threats to existing ECIES scheme, e.g. supporting new profiles/algorithms with PQC for SUCI calculations.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.1.3 MIKEY-SAKKE key exchange
| MIKEY-SAKKE is a key exchange method specified in the IETF RFC 6509 [6]. As described in TR 33.938 [2], it is used in the 3GPP system to securely transport cryptographic keys for Mission Critical Services [3]. It employs asymmetric cryptography for key distribution.
Assuming MIKEY-SAKKE will not be updated by IETF with PQC algorithms, alternative solutions should be studied for MIKEY-SAKKE due to post-quantum threats to existing signature schemes.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2 Solutions
| Editor’s Note: This clause contains solutions to update 3GPP defined security protocols (for example SUCI calculation) to use the appropriate PQC algorithm, if those protocols are not expected to be updated by other SDOs to use PQC algorithms.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1 Solutions to SUCI calculation
| Editor’s Note: If only SUCI calculation is considered, this subclause may be removed. If other protocol, e.g. MIKEY-SAKKE is studied, this subclause is used for each of such protocol identified.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.1 Solution #1 to SUCI calculation: SUCI calculation with PQC enhancement
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.1.1 Introduction
| It is proposed to introduce new SUCI calculation mechanism. The solution is applicable for SUCI calculation in ME.
Preassumption:
• ME supports PQC algorithms
• USIM indicates the SUCI calculation is done in ME
• USIM contains new public key for calculating SUCI with PQC
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.1.2 Solution details
| If the indication in USIM is the SUCI calculation should be done in ME, and operator’s decision is to use PQC to calculate the SUCI, then the public key for calculating SUCI using PQC shall be available in USIM. The ME read the SUPI, the SUPI Type, the Routing Indicator, the Home Network Public Key Identifier for PQC, the Home Network Public Key for PQC and the list of protection scheme identifiers. The ME shall select the protection scheme from its supported schemes that has the highest priority in the list are obtained from the USIM.
The alternative method is, there is no list of protection scheme identifiers, but only one identifier indicating UE to use PQC algorithm to calculate SUCI. UE will decide with algorithm to be used and attach it to the SUCI output. Network side will choose the same algorithm as the indication in SUCI and decode SUCI.
The candidate new profiles for SUCI may include below:
• ML-KEM [21]
Editor’s Note: Further details are FFS.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.1.3 Evaluation
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.2 Solution #2 to SUCI calculation: Solution on PQC for SUCI protection
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.2.1 Introduction
| The ECIES procedure as depicted by the 5G system architecture [21] is the basis for the development of the PQC solution.
For the transition to PQC the relevant functional blocks will have to replace the existing/corresponding ECIES functional blocks.
The following Figure depicts the Encryption based on ECIES at the UE side.
Figure 7.2.1.2.1-1: Encryption based on ECIES at the UE
The following Figure depicts the Decryption based on ECIES at the home network side.
Figure 7.2.1.2.1-2: Decryption based on ECIES at the Home Network
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.2.2 Solution details
| Editor’s Note: Details on the KDF are FFS
Editor’s Note: Details on how this solution could be used for hybrid PQC are FFS
Editor’s Note: Why is MAC verification after decryption is FFS.
Editor’s Note: Whether and how to support hybrid scheme is FFS.
Editor’s Note: Why relevant functional blocks have to replace existing/corresponding ECIES functional blocks is FFS.
The solution is replacing the ECIES functional blocks with corresponding/related PQC related functional blocks.
The following Figure depicts the PQC concept at the UE side. The functions which must be modified for the support of PQC are with green coloured background.
Figure 7.2.1.2.2-1: SUCI protection based on PQC algorithms at the UE side
At UE: PQC KEM public key of HN is used in Key encapsulation mechanism to generate ciphertext and shared secret. This shared secret is used as an input to Key Derivation Function (KDF) to generate the Encryption key to generate cipher text of SUPI and MAC value.
The following is applicable:
This step 1, as shown by the Figure 7.2.x.y.1-1, is for the transition to PQC not required, i.e., there is no creation of Ephemeral Keys needed in this concept.
2> The Kem Encapsulation Function will get the public key (pk) as input and is providing the cipher text (ct) and the shared secret (ss). The (ct) will be have to be send back to the network, whereas the (ss) will be used as input to the key derivation function.
3> The key derivation function is receiving the shared secret (ss) and is calculating the encryption key. There will be created a single key that is to be used for encryption and integrity protection.
4> The encryption is used for the computation of the encrypted plaintext block, i.e., ciphertext value.
5> The encryption is used for the computation of the MAC-I, i.e., MAC-tag value.
Both the ciphertext and the MAC-tag value will be included into the SUCI framework (see Figure 7.2.x.y.2-3) and will be sent to the Network for further treatment.
At Network side: The received PQC KEM cipher text is used along with the PQC KEM Secret key of HN (corresponding to received PQC KEM public key Id) to decapsulate and generate the shared secret. This shared secret is used as an input to KDF to generate the decryption key to decipher the cipher text and verify the MAC.
The following Figure depicts the PQC concept at the Network side.
Figure 7.2.1.2.2-2: SUCI protection based on PQC algorithms at the Home Network side
The following is applicable:
1> The Network side is retrieving the cipher text (ct) from the SUCI framework. The secret key (sk) is local stored and corresponds to the public key (pk) which has been share with UE. Both, the (ct) and the (sk) will be given as input to the Key Decapsulation function and the outcome is the shared secret (ss). The (ss) will be used as input to the key derivation.
2> The key derivation function is receiving the shared secret (ss) as input and is computing the decryption key. There will be created a single decrypt key that is to be used for decryption and integrity verification.
3> The decryption key is used for the computation of the Plaintext block.
4> The decryption key is used for the computation of the MAC-I verification.
If we apply this solution concept, then the SUCI framework is as depicted by below Figure.
Figure 7.2.x.y.2-3: SUCI framework for PQC
Home Network Public Key Identifier (PQC KEM) represents a public key provisioned by the HPLMN or SNPN and it is used to identify the key used for SUPI protection. Example of the PQC KEM Public key is Kyber (selected by NIST standards).
PQC KEM ciphertext: Post Quantum Cryptography Key encapsulation mechanism uses the PQC KEM public key of Home Network to generate the ciphertext.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.2.3 Evaluation
| TBD
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.3 Solution #3 to SUCI calculation: SUCI calculation with hybrid KEMs
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.3.1 Introduction
| This solution proposes a hybrid encryption approach with both PQC and traditional cryptography for SUCI calculation. The proposed solution uses two different KEM algorithms for key derivation.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.3.2 Solution details
| Editor’s Note: What is the advantage for presenting classical algorithm ECDH-KEM is ffs.
Editor’s Note: it is ffs whether there is no freshness aspect anymore as the stored key will be reused.
Editor’s Note: it is ffs how will the HN identify which key is used if there is no identifier.
Editor’s Note: it is ffs, for the MAC creation, there is no key used, this is just a hashing, not a keyed-hash.
Editor’s Note: SUCI size is ffs since with the c1c2 cipher text, new MAC, still SUCI size will be more than existing SUCI in 5G apart from the PQC addition.
Editor’s note: Details on how the MAC computation is performed are FFS.
Editor’s note: it is ffs the security issue introduced by using a non-keyed hash over part of the message.
Editor’s note: Why MAC on c1 and c2 is required is FFS.
The proposed solution is illustrated below. Figure 7.2.1.Y-1 shows the SUCI calculation at the UE. Figure 7.2.1.Y-2 shows the scheme output that the UE sends to the HN. Figure 7.2.1.Y-3 is the HN decryption of the SUCI from the UE.
Figure 7.2.1.3-1 SUCI calculation using hybrid KEM schemes at UE
1a. UE generates a shared key k1 and the corresponding ciphertext c1 based on the key encapsulation algorithm 1 (KEM1). The KEM1 uses ECDH-KEM with traditional cryptography as specified in NIST.SP.800-227 [73].
1b. UE generates a shared key k2 and the corresponding ciphertext c2 based on the key encapsulation algorithm 2 (KEM2). The KEM2 is PQC secure, and uses the ML-KEM-768 as specified in NIST FIPS 203 [21].
2a. UE generates a hybrid shared key (k) using KDF as specified in TS 33.501 [4], where k1||k2 is one of the inputs of the KDF.
2b. UE generates a MAC value 1 by hashing c1 and c2, e.g., MAC value 1 = SHA256 (c1||c2)
The MAC value 1 is used for the HN to verify correctness of c1 and c2 before performing the computation intensive cryptographic steps (e.g., steps 3-6 in Figure 7.2.1.Y-3).
3-5: UE continue with steps similar to the steps 3 -5 specified in clause C.3.2 in TS 33.501 [4].
The SUCI format generated by UE is as specified in TS 23.003 [74] and the Scheme Output as shown below includes the concatenation of the ciphertext c1||c2, MAC value 1, ciphertext c3 and MAC tag.
Figure 7.2.1.Y-2 The Scheme Output generated at the UE side
The processing of the received packet at the HN is shown in Figure 7.2.1.Y-3 with details as follows:
Figure 7.2.1.3-3 Decryption of SUCI at HN
1. HN verifies the received MAC value 1 of UE. If it succeeds, HN continues to perform the decapsulation of the shared key.
2a. HN decapsulates the shared key k1 based on the key encapsulation algorithm 1 (KEM1), the private key 1 of HN, and the received ciphertext c1 from UE. In the case of KEM1 = ECDH-KEM, ciphertext c1 is used as the ephemeral public key of the UE [75].
2b. HN decapsulates the shared key k2 based on the key encapsulation algorithm 2 (KEM2), the private key 2 of HN, and the received ciphertext c2 from the UE.
3. HN generates the shared key k in the same way at the UE side.
4-6: HN follows the steps 2-4 specified in clause C.3.3 of TS 33.501 [4].
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.3.3 Evaluation
| Editor’s note: Evaluation is FFS.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.4 Solution #4 to SUCI calculation: SUPI Pseudonym
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.4.1 Introduction
| This contribution proposes SUPI concealment using pseudonym instead of asymmetric encryption for SUPI.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.4.2 Solution details
| The Figure 7.2.1.4.2-1 illustrates the procedure:
Figure 7.2.1.4.2-1 procedure of using random number to do SUPI concealment
0. The UE and the UDM are pre-configured with the UE’s SUPI and a pseudonym, i.e., a random value RAND.
1. During registration, the UE uses the preconfigured pseudonym RAND as the UE's SUCI sent over the air interface.
2-3. The UDM/AUSF maps the pseudonym RAND to SUPI and complete the authentication using the SUPI. The RAND can also be reused as the RAND in the primary authentication.
4-5. After authentication, the UDM assigns a new pseudonym RAND' for the SUPI and sends it to the UE.
6. The UE uses the newly assigned pseudonym RAND' in the subsequent procedure.
Editor’s Note: it is ffs that RAND without binding to any UE specific key or encryption or MAC value will result in the attacker is just sending and RAND number blocking the genuine UE.
Editor’s Note: it is ffs that just the RAND can’t be used for routing of the information.
Editor’s Note: How does pre-configured pseudonym prevent traceability is FFS.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.4.3 Evaluation
| TBD
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.5 Solution #5 to SUCI calculation: Enhancement on SUCI calculations using quantum key
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.5.1 Introduction
| This solution provides enhancement for SUCI calculations to resolve post-quantum threats to existing ECIES scheme.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.5.2 Solution details
| This solution describes SUCI calculations using Quantum Channel. The UE can provision Public key of HN and Quantum Public Key. Based on ECIES scheme, the ephemeral public key, cipher text, and MAC tag can be generated as an output. Additionally, using the Quantum Public Key, the cipher text can be encapsulated. The encapsulated cipher text is delivered to the Home Network via Quantum Channel. The Home Network decapsulates it with Quantum private key, then deciphers ciphered text and verifies MAC.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.5.2.1 Processing on UE side
| The steps shown Figure 7.2.X.Y.2.1 are described as below:
0. As a prerequisite, the UE provisions both Public key of HN and Quantum Public key.
1. The UE generates Ephemeral key pair consisting of Ephemeral Public Key and Ephemeral Private Key.
2. Based on the generated Ephemeral Private Key and the Public key of Home Network, the UE generates Ephemeral Shared Key.
3. Using ECIES scheme, Ephemeral Encryption Key, ICB and Ephemeral MAC Key are generated.
4. Plaintext is ciphered using the Ephemeral Encryption Key.
5. The ciphered text and the Ephemeral MAC key are used to create MAC-tag value.
6. The ciphered text value is encapsuled using Quantum Public Key.
Figure 7.2.1.5.2.1: Encryption at UE
The final output shall be the concatenation of the ECC ephemeral public key, the Quantum encapsulated ciphertext value, the MAC tag value, and any other parameters, if applicable.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.5.2.2 Processing on home network side
| The steps shown Figure 7.2.1.5.2.2 are described as below:
1. By decapsulating the encapsulated cipher-text using Quantum Private Key, the Home Network generates the cipher-text.
2. Based on the received Ephemeral Public Key, the Home Network generates Ephemeral Shared Key.
3. Using ECIES scheme, Ephemeral Decryption Key, ICB and Ephemeral MAC Key are generated.
4. The ciphered text is deciphered using the Ephemeral Decryption Key.
5. The Home Network verifies received MAC.
Figure 7.2.1.5.2.2: Decryption at Home Network
Editor’s Note: Details on Step 6 at processing on UE side is FFS.
Editor’s Note: Details on Quantum Public key are FFS.
Editor’s Note: What is Quantum Channel is FFS.
Editor’s Note: Whether and how to support hybrid encryption.
Editor’s Note: Why SUCI should require a quantum channel into the HN is FFS.
Editor’s Note: What is a Quantum key and why it is required is FFS.
Editor's Note: The definition and usefulness of these terms for SUCI calculation are FFS: Post-quantum threat, Quantum channel, Quantum public key, Quantum-encapsulated, Quantum-encrypted, Quantum-ciphered, Quantum Private key.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.5.3 Evaluation
| TBD
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.6 Solution #6 to SUCI calculation: Enhancement on SUCI calculations using quantum encapsulated key
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.6.1 Introduction
| This solution provides enhancement for SUCI calculations to resolve post-quantum threats to existing ECIES scheme.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.6.2 Solution details
| This solution describes SUCI calculations using Quantum Channel. The UE can provision Public key of HN and Quantum Public Key. Based on ECIES scheme, the ephemeral public key and MAC tag can be generated as a part of output. To cipher plain text, The Ephemeral Encryption key is encapsulated using Quantum Public Key. Using the Quantum-encapsulated Ephemeral Encryption key, the Plaintext is quantum-encrypted. The cipher text is delivered to the Home Network via Quantum Channel. The Home Network decapsulates the received quantum-ciphered text using HN-generated Ephemeral decryption key. By decrypting it using Quantum Private key, The Home Network obtains plain text. Then verifies received MAC.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.6.2.1 Processing on UE side
| The steps shown Figure 7.2.1.6.2.1 are described as below:
7. As a prerequisite, the UE provisions both Public key of HN and Quantum Public key.
8. The UE generates Ephemeral key pair consisting of Ephemeral Public Key and Ephemeral Private Key.
9. Based on the generated Ephemeral Private Key and the Public key of Home Network, the UE generates Ephemeral Shared Key.
10. Using ECIES scheme, Ephemeral Encryption Key and Ephemeral MAC Key are generated.
11. The plain text and the Ephemeral MAC key are used to create MAC-tag value.
12. The Ephemeral Encryption Key is encapsulated using Quantum Public Key.
13. The Plaintext Block is encrypted using the Quantum Encapsulated Ephemeral Encryption Key.
Figure 7.2.1.6.2.1: Encryption at UE
The final output shall be the concatenation of the ECC ephemeral public key, the Quantum ciphertext value, the MAC tag value, and any other parameters, if applicable.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.6.2.2 Processing on home network side
| The steps shown Figure 7.2.1.6.2.2 are described as below:
6. Based on the received Ephemeral Public Key, the Home Network generates Ephemeral Shared Key.
7. Using ECIES scheme, Ephemeral Decryption Key and Ephemeral MAC Key are generated.
8. The Home Network decapsulates the received Quantum-ciphered text using the Ephemeral Decryption Key.
9. The Home Network decrypts the decapsulated Quantum-ciphered text using the Quantum Private Key. Then the Home network obtains the plain text.
10. The Home Network verifies received MAC. For the verification, plaintext and Ephemeral MAC key are utilized.
Figure 7.2.1.6.2.2: Decryption at Home Network
Editor’s Note: Details on Step 5 at processing on UE side is FFS.
Editor’s Note: How to sync of usage of Quantum keys at UE and HN sides is FFS.
Editor’s Note: Details on Quantum Public key are FFS.
Editor’s Note: Details on Step 3 at processing on HN side is FFS.
Editor’s Note: Whether the plaint text is encrypted with quantum public key (the Encryption figure at UE) is FFS.
Editor’s Note: Why SUCI should require a quantum channel into the HN is FFS.
Editor’s Note: What is a Quantum key and why it is required is FFS.
Editor’s Note: How this solution is different from the solution in S3-253475 is FFS.
Editor's Note: The definition and usefulness of these terms for SUCI calculation are FFS: Post-quantum threat, Quantum channel, Quantum public key, Quantum-encapsulated, Quantum-encrypted, Quantum-ciphered, Quantum Private key.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.6.3 Evaluation
| TBD
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7 Solution #7 to SUCI calculation: SUCI calculations
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.1 Introduction
| Annex C of TS 33.501 [4] specifies two protection schemes for concealing a SUPI into a SUCI. The protection schemes are called Profile A and Profile B. These two profiles use SECG ECIES [9], which is a so called KEM-DEM scheme — combining a Key Encapsulation Mechanism (KEM) and a Data Encapsulation Mechanism (DEM). SECG is unlikely to update its specifications. PQC migration of SUCI calculations does not require changing any protocols or architectures — it is sufficient to introduce new SUCI profiles.
Editor’s note: It is FFS whether the additional optional inputs to Key Combine which are sent in cleat text over the air can enhance security.
Editor’s note: For easier understanding, further details on how to implement the solution (e.g., the schematic figures as in 33501 and call flows) is FFS.
Editor’s note: For easier understanding, further details on hybrid keys and how hybrid scheme is realized is FFS.
Editor's note: Justification for mixing different security levels, i.e., ML-KEM-768 with AES-256, is FFS.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.2 Solution details
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.2.1 General
| PQC migration for SUCI calculations can be done by introducing new SUCI profiles, and the new SUCI profiles can be created by extending the existing SUCI profiles with simple algorithm updates. Using such extensions is not a new thing to do. It was also the case when 5G was specified — following recommendations from ETSI SAGE, 3GPP not only profiled SECG ECIES, but also extended it to support Montgomery curves like Curve25519, along with HMAC-SHA-256 (with 64-bit long tag).
Adding a PQC KEM (hybrid or standalone) is equally straightforward. Though the “EC” in ECIES gives the impression that it must use an elliptic curve, there are no technical obstacles to replacing the elliptic curve-based KEM in ECIES with either a standalone or a hybrid PQC KEM. It is similar to how TLS 1.3 continues to refer to KEM algorithms as the underlying algebraic groups and KEM encapsulations as KeyShares.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.2.2 ML-KEM is the Most Suitable Option
| ML-KEM is already standardized, and its implementations are widely available. During the specification of SUCI protection in 33.501 [4], SA3 had considered the future need for PQC and therefore specified a maximum SUCI length of 3000 bytes to allow the introduction of quantum-resistant protection schemes. NIST has now standardized the lattice-based ML-KEM in FIPS 203 [21] and, as it was expected, both standalone and hybridized ML-KEM-512, ML-KEM-768, and ML-KEM-1024 fit in 3000 bytes.
Since Rel-15, IETF has specified HPKE — while ECIES is a pure KEM-DEM scheme, parts of HPKE requires Diffie-Hellman and cannot be implemented with a KEM. Besides, HPKE provides no clear benefits for SUCI calculations. In fact, for a fixed tag length, GCM provides worse integrity properties than HMAC-SHA2 and KMAC, which is the reason why ETSI SAGE has specified GCM-SST [76] for use in 6G. Using HPKE would also give up change control to the IETF.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.2.3 Considerations for Hybrid KEM
| When using a hybridized PQC KEM with ML-KEM, it is essential to use a standardized key combiner that preserves the IND-CCA2 security of ML-KEM, hybridization must not weaken the security properties. While ML-KEM is currently the only practical option, the key combiner should be designed in a general way so that the same construction can be reused in future profiles with other KEMs beyond ML-KEM. Additional KEMs may be introduced in proprietary profiles or standardized by 3GPP in the future. Two standardized and compatible IND-CCA2 key combiners are specified in Section 4.6 of SP 800-227 [73] and Section 8.2 of ETSI TS 103 744 [30]. Below is equation (9) from SP 800-227 [73], which focuses on the information elements:
K ← KeyCombine(K1, K2, c1, c2, ek1, ek2, p)
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.2.4 KDF, MAC, and Encryption
| Any implementation of ML-KEM [21] already support of SHA3-256, SHA3-512, SHAKE128, and SHAKE256, which ML-KEM uses natively — therefore, using SHA-3 for key derivation and MAC in PQC SUCI is a natural choice. Also, SEC1 standard [9], specifying ECIES, published in 2009, says that future versions of the standard are likely to allow SHA3. Moreover, SHA-3 is theoretically (random oracle and no length extension attacks) and practically (strong side-channels resistance and simplicity) superior to SHA-2 [77]. Considering the ongoing work on 256-bit and AEAD study, all PQC SUCI profiles should use AES-256 for encryption.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.2.5 New SUCI Profiles
| This solution proposes that the 3GPP SUCI profiles in TS 33.501 [4] should be updated to include profiles for both standalone ML-KEM and ML-KEM hybridized with X25519 — both fit into the designed length limit (3000 bytes). These profiles should use algorithms from the SHA-3 family (e.g., SHA3-256, KMAC256) [31, 32], both for the MAC and in the KDF.
Below are two suggested profiles, with the formatting intentionally left out.
Standalone ML-KEM Profile:
The parameters for this profile shall be the following:
- KEM domain parameters : ML-KEM-768
- KEM primitive : ML-KEM-768
- point compression : N/A
- KDF : ANSI-X9.63-KDF [9]
- Hash : SHA3-256
- SharedInfo1 : ML-KEM encapsulation (ciphertext)
- MAC : KMAC256
- mackeylen : 32 octets (256 bits)
- maclen : 8 octets (64 bits)
- SharedInfo2 : the empty string
- ENC : AES–256 in CTR mode
- enckeylen : 32 octets (256 bits)
- icblen : 16 octets (128 bits)
- backwards compatibility mode : false
Hybrid ML-KEM Profile:
The parameters for this profile shall be the following:
- KEM domain parameters : ML-KEM-768 + X25519
- KEM primitive : ML-KEM-768 + X25519
- point compression : N/A
- KDF : ANSI-X9.63-KDF [9]
- Hash : SHA3-256
- SharedInfo1 : Combine(c1, c2, ek1, ek2, p)
- MAC : KMAC256
- mackeylen : 32 octets (256 bits)
- maclen : 8 octets (64 bits)
- SharedInfo2 : the empty string
- ENC : AES–256 in CTR mode
- enckeylen : 32 octets (256 bits)
- icblen : 16 octets (128 bits)
- backwards compatibility mode : false
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.7.3 Evaluation
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.8 Solution #8 to SUCI calculation: GSMA-based solution
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.8.1 Introduction
| GSMA published guidelines "Post Quantum Cryptography – Guidelines for Telecom Use Cases – v2.0" [33] to support the planning, setup and execution of a quantum safe cryptography journey for telco industry. This GSMA report contains a detailed analysis of an initial set of Telcom use cases that are impacted by Post Quantum Cryptography. Concealment of the Subscriber Public Identifier is one of the analysed use cases.
An additional security enhancement is proposed to the solution described in GSMA guidelines [33].
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.8.2 Solution details
| The solution for concealment of the Subscriber Public Identifier is based on the hybridization between ML-KEM (Level 3) and classic ECC based key exchanged algorithms that is described in clause 5.8 of GSMA guidelines [33].
GSMA solution is enhanced thanks to the addition of Post Quantum ciphertext as input to the Key Derivation Function in the Post Quantum Cryptography part, as recommended to obtain IND-CCA (indistinguishability under chosen-ciphertext attack) property for KEM.
Processing on UE side:
Processing on home network side
Profiles
The associated updated profiles are the following ones. In both cases, the Key Derivation Function (KDF) outputs a L-bytes string that must be parsed as Eph Encryption key || ICB || Eph. Mac Key, where Eph Encryption key is of size enkeylen, ICB is of size icblen, and Eph. Mac Key is of size mackeylen.
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d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.8.2.1 Profile A’ (update of Profile A to support PQC algorithm)
| The ME and SIDF shall implement this profile. The parameters for this profile shall be the following:
- KEM domain parameters : ML-KEM-768 [21]
- EC domain parameters : Curve25519
- KEM primitive : ML-KEM-768 [21]
- EC Diffie-Hellman primitive : X25519
- point compression : N/A
- KDF : HMAC-based KDF RFC 5869 [34] (SHA-256)
- Hash : SHA-256
- KDF inputs (see RFC 5869 [34] terminology):
-salt : empty
-IKM (input key material) : Eph. shared key1 || Eph. shared key 2
-Info : Post-Quantum Ciphertext || Eph. Public key
-L (output length in octets) : 80
- MAC : HMAC–SHA-256
- mackeylen : 32 octets (256 bits)
- maclen : 16 octets (128 bits)
- SharedInfo2 : the empty string
- ENC : AES-256 in CTR mode
- enckeylen : 32 octets (256 bits)
- icblen : 16 octets (128 bits)
- backwards compatibility mode : false
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.8.2.2 Profile B’ (update of Profile B to support PQC algorithm)
| The ME and SIDF shall implement this profile. The parameters for this profile shall be the following:
- KEM domain parameters : ML-KEM-768 [21]
- EC domain parameters : secp256r1
- KEM primitive : ML-KEM-768 [21]
- EC Diffie-Hellman primitive : Elliptic Curve Cofactor Diffie-Hellman Primitive
- point compression : true
- KDF : HMAC-based KDF RFC 5869 [34] (SHA-256)
- Hash : SHA-256
- KDF inputs (see RFC 5869 [34] terminology):
-salt : empty
-IKM (input key material) : Eph. shared key1 || Eph. shared key 2
-Info : Post-Quantum Ciphertext || Eph. Public key
-L (output length) : 80
- MAC : HMAC–SHA-256
- mackeylen : 32 octets (256 bits)
- maclen : 16 octets (128 bits)
- SharedInfo2 : the empty string
- ENC : AES-256 in CTR mode
- enckeylen : 32 octets (256 bits)
- icblen : 16 octets (128 bits)
- backwards compatibility mode : false
Editor’s Note: It is FFS whether the additional inputs to KDF which are sent in cleat text over the air can enhance security.
Editor’s Note: Reasons for using c1c2 as the input for the KDF are FFS.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.8.3 Evaluation
| TBD
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9 Solution #9 to SUCI calculation: SUPI Concealment using PQC Shared Key
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9.1 Introduction
| To counter the threat of quantum computing to asymmetric cryptography used in ECIES scheme it is necessary to replace existing algorithms with new, quantum-resistant Post Quantum Cryptography (PQC) ML-KEM algorithms proposed by NIST [21].
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9.2 Solution details
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9.2.1 Processing on UE side
| The PQC shared key generation scheme is implemented such that for computing a fresh SUCI, the UE uses the provisioned PQC-based public key of the home network, and PQC-based key encapsulation mechanism (KEM) according to the parameters provisioned by home network. The processing on UE side is done as mentioned below.
1. UE generates an ephemeral shared key and an encrypted PQC shared key based on a PQC-based public key associated with the home network.
2. UE generates ephemeral symmetric encryption key and ephemeral MAC key using a KDF function and ephemeral shared key.
3,4. UE protects the plaintext block (i.e. SUPI or UE ID), using the encryption key and the MAC key. The final output is the concatenation of encrypted PQC shared key, the ciphertext (i.e., Enc(SUPI)) value, and MAC tag value.
The Figure 7.2.1.9.2-1 illustrates the UE's steps.
Figure 7.2.1.9.2-1: Encryption based on PQC shared key generation at UE
Finally, the proposed solution comprises transmitting the encrypted PQC shared key along with cipher-text value and MAC-tag value associated with the subscriber by the UE to a network entity for authenticating the subscriber. The scheme output as defined in TS 23.003 [74] to be updated to scheme output shown in Figure 7.2.1.9.2-2.
Figure 7.2.1.9.2-2: Scheme output based on SUPI concealment using PQC shared key
NOTE: Ciphertext output from PQC key encapsulation is referred to as encrypted PQC shared key as there is another ciphertext value from step 3 of symmetric encryption, to avoid confusion.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9.2.2 Processing on home network side
| The PQC shared key generation scheme is implemented such that for deconcealing a SUCI, the home network uses the received encrypted PQC shared key, and the PQC-based private key of the home network.
1. Home network (HN) decapsulates the encrypted PQC shared key to derive the ephemeral shared key.
2. HN generates ephemeral symmetric encryption key and ephemeral MAC key using a KDF function and derived ephemeral shared key.
3,4. HN verifies the MAC and decrypts the ciphertext to derive the plaintext block (i.e. SUPI or UE ID), using the MAC key and encryption key respectively.
Figure 7.2.1.9.2-3 illustrates the home network's steps.
Figure 7.2.1.9.2-3: Decryption based on PQC shared key generation at home network
NOTE: Ciphertext input to PQC key decapsulation is referred to as encrypted PQC shared key as there is another ciphertext value to step 3 of symmetric decryption, to avoid confusion.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9.2.2 Sample profile for SUCI Calculation
| Profile C uses ML-KEM as defined in [21] to generate shared key Z1 integrated with AES encryption scheme.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9.2.2.1 Profile C (PQC only)
| The ME and SIDF implement this profile. The parameters for this profile are the following:
- ML KEM parameters : Level 3 (k, lattice dimension 3)
- KDF : ANSI-X9.63-KDF [9]
- Hash : SHA-256
- Shared secret key Z1 : Shared secret field from ML-KEM
- MAC : HMAC–SHA-256
- mackeylen : 32 octets (256 bits)
- maclen : 8 octets (64 bits)
- SharedInfo1 : N/A
- SharedInfo2 : the empty string
- ENC : AES–256 in CTR mode
- enckeylen : 32 octets (256 bits)
- icblen : 32 octets (256 bits)
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.9.3 Evaluation
| TBD
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.10 Solution #10 to SUCI calculation: SUPI Concealment using Hybrid shared Key
| Editor’s Note: Details on KDF inputs are FFS.
Editor's Note: The pros and cons (including security, complexity and efficiency) of combining traditional asymmetric cryptographic algorithms with post-quantum cryptographic algorithms for SUCI calculation is FFS.
Editor’s Note: Why to use an ad-hoc KEM combiner instead of adding a standard KEM combiner is FFS.
Editor’s Note: Detailed profiles needs to update later including other options.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.10.1 Introduction
| Replacing classical cryptography with PQC algorithms at an early stage carries an inherent risk as a first time widespread deployment and more rigorous testing of PQC algorithms may be needed. So it will be beneficial to have it integrated with classical asymmetric cryptography based security mechanisms via a hybrid approach, where both classical asymmetric algorithms and post-quantum algorithms coexist. The main objective of a hybrid shared key generation mechanism is to enable the creation of a secure shared secret that remains protected as long as at least one of its underlying key exchange components remains uncompromised. In case vulnerabilities are found in either type of algorithm, the presence of both classical and post-quantum algorithms in a hybrid setup reduces the impact of potential breaches, providing additional resilience to the overall cryptography.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.10.2 Solution details
| |
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.10.2.1 Processing on UE side
| The Hybrid shared key generation scheme is implemented such that for computing a fresh SUCI, the UE uses the provisioned EC based public key of the home network, provisioned PQC-based public key of the home network, freshly generated ECC (elliptic curve cryptography) ephemeral public/private key pair and PQC-based key encapsulation mechanism (KEM) according to the parameters provisioned by home network. The processing on UE side is done as mentioned below.
1. UE generates an ephemeral EC public key and an ephemeral EC private key at UE with Elliptical Curve (EC) key generation function.
2. UE generates a first ephemeral shared key (s1) based on the ephemeral EC private key of UE and an EC based home network public key.
3. UE generates a second ephemeral PQC shared key (s2) and an encrypted PQC shared key based on a PQC-based public key associated with the home network using ML-KEM [aa].
4. UE generates an ephemeral hybrid shared key based on the first ephemeral shared key and the second ephemeral shared key using methods like concatenation.
5. UE generates ephemeral symmetric encryption key and ephemeral MAC key using a KDF function and ephemeral hybrid shared key.
6. UE protects the plaintext block (i.e. SUPI or UE ID), using the encryption key and the MAC key. The final output is the concatenation of the ECC ephemeral public key, the encrypted PQC shared key, the ciphertext value, the MAC tag value.
Figure 7.2.1.10.2-1 illustrates the UE's steps.
Figure 7.2.1.10.2-1: Encryption based on Hybrid shared key generation at UE
Finally, the proposed solution comprises transmitting the encrypted PQC shared key along with the ephemeral public key of UE, the encrypted PQC shared key, the cipher-text value, and the MAC-tag value associated with the subscriber by the UE to a network entity for authenticating the subscriber. The scheme output as defined in TS 23.003 [74] to be updated to scheme output shown in Figure 7.2.X.Y.2-2.
Figure 7.2.1.10.2-2: Scheme output based on Hybrid PQC-based SUPI concealment
NOTE: Ciphertext output from PQC key encapsulation is referred to as encrypted PQC shared key as there is another ciphertext value from step 3 of symmetric encryption, to avoid confusion.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.10.2.2 Processing on home network side
| The Hybrid shared key generation scheme is implemented such that for deconcealing a SUCI, the home network uses the received ECC ephemeral public key of the UE, encrypted PQC shared key, EC based private key of the home network and the PQC-based private key of the home network.
1. Home network (HN) generates a first ephemeral shared key (s1) based on the ephemeral EC public key, received from UE, and an EC based home network private key.
2. HN decapsulates the encrypted PQC shared key, received from UE, to derive the second ephemeral shared key (s2) using ML-KEM [aa].
3. HN generates an ephemeral hybrid shared key based on the first ephemeral shared key (s1) and the second ephemeral shared key (s2) using methods like concatenation.
4. HN generates ephemeral symmetric encryption key and ephemeral MAC key using a KDF function and ephemeral hybrid shared key.
5. HN verifies the MAC and decrypts the ciphertext to derive the plaintext block (i.e. SUPI or UE ID), using the MAC key and encryption key respectively.
Figure 7.2.1.10.2-3 illustrates the home network's steps.
Figure 7.2.1.10.2-3: Decryption based on Hybrid shared key generation at home network
NOTE: Ciphertext input to PQC key decapsulation is referred to as encrypted PQC shared key as there is another ciphertext value to step 3 of symmetric decryption, to avoid confusion.
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.10.2.3 Sample Profiles for SUCI calculation
| Profile C uses Post-Quantum Traditional (PQ/T) hybrid scheme as defined in RFC 9794 [7] which is a multi-algorithm scheme where at least one component algorithm is a post-quantum algorithm and at least one is a traditional algorithm. The traditional algorithm component uses its own standardized processing for key generation (section 6 of RFC 7748 [35]) and shared secret calculation (section 5 of RFC 7748 [35]). The Diffie-Hellman primitive X25519 (section 5 of RFC 7748 [35]) takes two random octet strings as input, decodes them as scalar and coordinate, performs multiplication, and encodes the result as an octet string. The shared secret output octet string from X25519 is used as the input Z in the ECIES KDF (section 3.6.1 of [9]). The post-quantum algorithm component of PQ/T scheme uses ML-KEM as defined in [aa]. Final shared secret key Z1 is derived from combining Z and shared secret generated from ML-KEM [aa]. Use the key derivation function KDF to generate keying data K of length enckeylen + icblen + mackeylen octets from Z1 and [SharedInfo1]. As the point compression is not applied for profile C, the prefix rule for compression type defined in [9] section 5.1.3 is not be used in profile C, i.e., there is no prefix for the ephemeral public key of Profile C.
Profile D uses Post-Quantum Traditional (PQ/T) hybrid scheme as defined in RFC 9794 [7] which is a multi-algorithm scheme where at least one component algorithm is a post-quantum algorithm and at least one is a traditional algorithm. The traditional algorithm component uses point compression to save overhead and use the Elliptic Curve Cofactor Diffie-Hellman Primitive (section 3.3.2 of [9]) to enable future addition of profiles with cofactor h ≠ 1. For curves with cofactor h = 1 the two primitives (section 3.3.1 and 3.3.2 of [9]) are equal. The post-quantum algorithm component of PQ/T scheme uses ML-KEM as defined in [aa]. Final shared secret key Z1 is derived from combining Z and shared secret generated from ML-KEM [aa]. Use the key derivation function KDF to generate keying data K of length enckeylen + icblen + mackeylen octets from Z1 and [SharedInfo1].
|
d20b4aa3005bbe8602412746b3658946 | 33.703 | 7.2.1.10.2.3.1 Profile C (Hybrid 1)
| The ME and SIDF implement this profile. The parameters for this profile are the following:
- Identifier : X25519MLKEM768 (Combining X25519 ECDH with ML-KEM-768)
- EC domain parameters : Curve25519 [35]
- EC Diffie-Hellman primitive : X25519 [35]
- point compression : N/A
- ML-KEM parameters : Level 3 (k, lattice dimension 3)
- KDF : ANSI-X9.63-KDF [9]
- Hash : SHA-256
- SharedInfo1 : (the ephemeral public key octet string – see [9] section 5.1.3)
- Shared secret key Z1 : Z (see [9] section 5.1.3) || Shared secret field from ML-KEM
- MAC : HMAC–SHA-256
- mackeylen : 32 octets (256 bits)
- maclen : 8 octets (64 bits)
- SharedInfo2 : the empty string
- ENC : AES–256 in CTR mode
- enckeylen : 32 octets (256 bits)
- icblen : 32 octets (256 bits)
|
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