7 Cryptographic Foundations
7.1 Security Assumptions
AMATELUS relies on the following cryptographic security assumptions:
Collision-resistant hash: SHA3-512 provides 128-bit security against quantum adversaries
Unforgeable signatures: Dilithium2 provides 128-bit security against quantum adversaries
ZKP soundness: Standard zero-knowledge properties (completeness, soundness, zero-knowledge)
7.2 Threat Model and Mitigations
7.2.1 Impersonation Attack (Different Secret Key)
Under signature unforgeability and proof soundness, verify both communication key control and the signed claim’s relationship to that presenter. A known public key alone does not connect an independently valid attribute proof to its sender. Issuer-approved subject links and the expected request context must also be checked.
7.2.2 Replay Attack (Same ZKP, Same User)
Replay prevention combines service-owned challenge state with protocol-enforced binding of the proof to the expected presentation context.
Important distinction:
Impersonation attacks (attacker with different secret key): require authenticated transport plus claim/subject/key/context binding
Replay attacks (legitimate user reusing same ZKP): implemented by the service. Interactive and AHI profiles require fresh challenges; AMATELUS proof verification must enforce the expected context binding.
Interactive/authorization profiles must implement challenge handling at the application layer:
Generate unique session nonces for each verification
Record and verify nonce freshness (checking that the nonce has not been used before)
Maintain nonce history in application database
An explicitly reusable attestation may omit fresh-session semantics. Interactive age checks, permission checks and one-time grants require fresh challenges.
7.2.3 Man-in-the-Middle Attack
Man-in-the-Middle attacks are mitigated at the transport layer.
While AMATELUS provides cryptographic identity verification, ECDH-1PU authenticated encryption and TLS/HTTPS are the responsibility of service providers.
7.2.4 Sybil Attack (Multiple DIDs)
Multiple DID possession is intentional protocol design for privacy protection.
While a single entity can control multiple DIDs, Anonymous Hash Identifiers (AHI) restrict per-audit-domain abuse through cryptographic binding to national identity systems.