webauthn-crypto-api

Contract layer for cryptographic and trust operations used by validation and ceremony services.

What it provides

• RpIdHasher, SignatureVerifier, AttestationVerifier, TrustAnchorSource contracts
• A vendor-neutral seam between validation/orchestration and concrete crypto backends
• A stable place to plug your own cryptography or trust policy implementation

When to use

• You are implementing custom crypto or attestation behavior.
• You want server logic to depend on interfaces, not provider details.
• You are building an alternative to webauthn-server-jvm-crypto.

How to use

import dev.webauthn.crypto.RpIdHasher
import dev.webauthn.model.RpIdHash

fun rpIdHasher(sha256: (ByteArray) -> ByteArray): RpIdHasher {
    return RpIdHasher { rpId ->
        val rpIdSha256 = sha256(rpId.encodeToByteArray())
        RpIdHash.fromBytes(rpIdSha256)
    }
}

Real-world scenario: multi-tenant backends can swap verifier and trust-anchor strategy per tenant while keeping ceremony services unchanged.

How it fits

flowchart LR
    CORE["webauthn-core"] --> API["webauthn-crypto-api contracts"]
    SERVER["webauthn-server-core-jvm"] --> API
    JVM["webauthn-server-jvm-crypto"] --> API
    MDS["webauthn-attestation-mds"] --> API

Pitfalls and limits

• Contract ownership stays here; concrete security posture is in your implementation.
• Incorrect hashing, signature-verification, or trust-anchor implementations weaken validation guarantees.
• Kotlin consumers that enable -Xreturn-value-checker=check are warned when crypto or trust results are ignored.

Status

Beta, vendor-agnostic contract layer.