Crate evidence 

Type-level tags for cryptographic primitives.

evidence provides wrapper types like Digest<T, P, C>, Signed<T, S, C>, and Encrypted<T, E, C> that wrap cryptographic output (hashes, signatures, ciphertext) with phantom type parameters encoding type-level information about them. The parameters are never stored at runtime — they exist only at compile time to prevent misuse:

• T tracks what was hashed, signed, or encrypted
• P/S/E tracks which algorithm was used (e.g., SHA-256, Ed25519)
• C tracks how the value was serialized before the operation

Because these parameters are part of the type, the compiler rejects mistakes like comparing a Digest<User, Sha256, _> to a Digest<Post, Sha256, _>, or verifying a signature against the wrong key type — all at zero runtime cost.

Digest Example

use evidence::digest::{Digest, sha2::Sha256};
use evidence::codec::Identity;

// Distinct types for different data
struct User([u8; 4]);
struct Post([u8; 4]);

impl AsRef<[u8]> for User {
    fn as_ref(&self) -> &[u8] { &self.0 }
}

impl AsRef<[u8]> for Post {
    fn as_ref(&self) -> &[u8] { &self.0 }
}

let user = User([1, 2, 3, 4]);
let post = Post([5, 6, 7, 8]);

// These are different types — can't be mixed up!
let user_hash: Digest<User, Sha256, Identity> = Digest::hash(&user);
let post_hash: Digest<Post, Sha256, Identity> = Digest::hash(&post);

// Compile error if uncommented: mismatched types
// let _: Digest<User, Sha256, Identity> = post_hash;

Cargo Features

All features are opt-in. No features are enabled by default.

Feature	Provides
sha2	Sha256, Sha384, Sha512
sha3	Sha3_224, Sha3_256, Sha3_384, Sha3_512, Keccak256, Keccak512
blake3	Blake3
ed25519	Ed25519 signature primitive + Signer/AsyncSigner impl
hmac	HmacSha256, HmacSha384, HmacSha512
chacha20poly1305	ChaCha20Poly1305 AEAD
aes-gcm	Aes128Gcm, Aes256Gcm AEAD
minicbor	Cbor codec Encode/Decode impls
serde_json	Json codec Encode/Decode impls (requires std)
serde	Serialize/Deserialize impls
rkyv	Zero-copy Archive/Serialize/Deserialize impls
arbitrary	Arbitrary impl for fuzzing
bolero	TypeGenerator impl for bolero
proptest	Arbitrary impl for proptest (requires std)

Signature Example

use evidence::{codec::Identity, signature::{ed25519::Ed25519, Signer}, signed::Signed, verified::Verified};

let signing_key = ed25519_dalek::SigningKey::from_bytes(&[1u8; 32]);
let data = b"hello world";

// Sign the data
let signed: Signed<[u8; 11], Ed25519, Identity> = Signed::seal(&signing_key, data);

// Payload is inaccessible until verified
let verified: Verified<[u8; 11], Ed25519, Identity> = signed.try_verify().unwrap();
assert_eq!(verified.payload(), data);

Modules

codec

Codec traits for encoding and decoding values.

digest

Content-addressed digests with phantom type tracking.

encrypted

Encrypted payloads with type-level tracking.

encryption

Encryption primitives and traits.

fingerprint

Content-addressed fingerprints (truncated digests).

mac

Message Authentication Codes with type-level tracking.

signature

Signature primitives and signer traits.

signed

Signed payloads with type-level tracking.

verified

Verified payloads — witnesses of successful signature verification.