C2SP signed-note verification and signing.
A signed note is a UTF-8 text body followed by one or more signature lines, as defined by the C2SP signed-note spec. This engine supports two signature types:
- Ed25519 — the classical C2SP signature type.
- Metamorphic hybrid — an additive composite (
ML-DSA+Ed25519, strict-AND verify) that wedges post-quantum integrity into the same note format. ML-DSA signing is hedged/randomized, so signature bytes are not reproducible, but verification is fully deterministic.
verify/2 takes the note text and a list of trusted verifier keys (the
C2SP name+hash+base64key encoding). Unknown-key signatures are ignored; a
signature from a known key that fails rejects the whole note.
Summary
Functions
Sign text with a raw 32-byte Ed25519 seed (base64), returning the complete
classical (witness-compatible) C2SP signed-note text.
Sign text with an additive hybrid PQ composite secret key, returning the
complete C2SP signed-note text (body + blank line + the hybrid signature
line).
Boolean form of verify/2. Returns true if at least one trusted key signed
and verified.
Verify note_text against trusted_vkeys.
Functions
@spec sign_ed25519(text :: String.t(), name :: String.t(), seed_b64 :: String.t()) :: {:ok, String.t()} | {:error, String.t()}
Sign text with a raw 32-byte Ed25519 seed (base64), returning the complete
classical (witness-compatible) C2SP signed-note text.
text must be the exact note body ending in a newline. name is the C2SP
key name; seed_b64 is the base64 32-byte Ed25519 seed. Returns
{:ok, note_text} or {:error, reason} (invalid name or a seed that is not
32 bytes).
@spec sign_hybrid( text :: String.t(), name :: String.t(), secret_key_b64 :: String.t() ) :: {:ok, String.t()} | {:error, String.t()}
Sign text with an additive hybrid PQ composite secret key, returning the
complete C2SP signed-note text (body + blank line + the hybrid signature
line).
text must be the exact note body ending in a newline. name is the
C2SP key name; secret_key_b64 is the base64 metamorphic-crypto composite
secret key. ML-DSA signing is hedged, so the signature bytes are not
reproducible — but the verifier key derived from secret_key_b64's public
half (see MetamorphicLog.VerifierKey.encode_hybrid/2) verifies the result
deterministically.
Returns {:ok, note_text} or {:error, reason} (invalid name, undecodable
secret key, or signing failure).
Example
{:ok, note} = MetamorphicLog.Note.sign_hybrid("origin/log\n7\ncm9vdA==\n", "origin/log", sk)Boolean form of verify/2. Returns true if at least one trusted key signed
and verified.
@spec verify(note_text :: String.t(), trusted_vkeys :: [String.t()]) :: {:ok, non_neg_integer()} | {:error, String.t()}
Verify note_text against trusted_vkeys.
Returns {:ok, verified_count} — the number of trusted signatures that
verified (always ≥ 1 on success) — or {:error, reason} (including
"no trusted signature" when none of the trusted keys signed).
Example
{:ok, 1} = MetamorphicLog.Note.verify(note_text, [vkey])