RFC 8032: Edwards-Curve Digital Signature Algorithm (EdDSA)
IRTF/CFRG specification of EdDSA deterministic Schnorr signatures over twisted Edwards curves, defining Ed25519 (SHA-512) and Ed448 (SHAKE256), with encoding, verification, and test vectors.
Overview
RFC 8032, “Edwards-Curve Digital Signature Algorithm (EdDSA),” is an IRTF Crypto Forum Research Group (CFRG) informational specification by S. Josefsson and I. Liusvaara, published January 2017. It gives an implementation-oriented description of EdDSA, a variant of Schnorr’s signature scheme built on (possibly twisted) Edwards curves. The document defines two concrete instances, Ed25519 and Ed448, and supplies parameter choices, encoding rules, signing and verification procedures, sample Python code, and extensive test vectors.
Key points
- EdDSA is a deterministic Schnorr-style signature scheme: the per-signature nonce is derived by hashing the private key and message, removing the dependence on a high-quality random number generator that has repeatedly broken ECDSA implementations.
- Ed25519 targets roughly 128-bit security over the edwards25519 curve using SHA-512, with 32-octet public keys and 64-octet signatures; Ed448 targets roughly 224-bit security over edwards448 using SHAKE256, with 57-octet keys and 114-octet signatures.
- Complete (exception-free) Edwards addition formulas apply to all curve points, avoiding special-case branches and improving resistance to side-channel attacks and implementation errors.
- PureEdDSA (Ed25519, Ed448) is collision-resilient: a hash-function collision does not by itself break the signature. HashEdDSA variants (Ed25519ph, Ed448ph) prehash the message for single-pass streaming, and Ed25519ctx adds a domain-separating context string.
- The specification is deliberately implementation-focused, pairing precise octet-level encoding of points and scalars with reference code and test vectors so independent implementations can interoperate.
Relevance to Truestamp
Truestamp uses Ed25519 signatures (the primary RFC 8032 instance) to sign proof material, making this RFC the authoritative reference for that signing scheme. See Ed25519 signatures and the Ed25519 signature glossary term.
Citations
- RFC 8032: Edwards-Curve Digital Signature Algorithm (EdDSA). S. Josefsson and I. Liusvaara, IRTF CFRG, January 2017.