Overview

EdDSA (Edwards-curve Digital Signature Algorithm) is a public-key digital signature scheme built on twisted Edwards curves, using a variant of the Schnorr signature. It was designed by Daniel J. Bernstein, Niels Duif, Tanja Lange, Peter Schwabe, and Bo-Yin Yang, first published in 2011, with a public-domain reference implementation. Its stated goals are high speed and high security together, with strong resistance to implementation pitfalls that have broken earlier signature schemes. This Wikipedia article describes the scheme, its parameters, and its two standardized instantiations, Ed25519 and Ed448.

Key points

• EdDSA operates over an elliptic-curve group whose order is 2^c * l, where l is a large prime; security relies on l exceeding roughly 2^200 to resist discrete-logarithm attacks such as Pollard’s rho.
• Nonces are generated deterministically as a hash of part of the private key and the message, eliminating the reliance on a secure random-number generator per signature. Bad randomness famously exposed ECDSA keys (for example the Sony PlayStation 3 key compromise).
• Ed25519 uses the SHA-512 hash and a Curve25519-related curve over the field q = 2^255 - 19, yielding 32-byte (256-bit) public keys, 64-byte (512-bit) signatures, and about 128-bit security.
• Ed448 uses the SHAKE256 hash and a Curve448-related Edwards curve for a higher security level, and is specified alongside Ed25519 in IETF RFC 8032.
• The design avoids branches and array indices that depend on secret data, mitigating timing and other side-channel attacks.
• EdDSA is standardized in RFC 8032 and NIST FIPS 186-5 (2023, which adds deterministic Ed25519), and for SSH in RFC 8709; Ed25519 is widely deployed in OpenSSH, GnuPG, libsodium, OpenSSL, and other libraries.

Relevance to Truestamp

Truestamp signs its blockchain blocks and proof material with Ed25519, the primary EdDSA instantiation this source documents, so the scheme’s deterministic-nonce and side-channel properties underpin the integrity of Truestamp signatures. See Ed25519 signatures and the Ed25519 signature glossary term.

Citations

1. EdDSA (Wikipedia). Wikipedia contributors; scheme originally published 2011 by Bernstein, Duif, Lange, Schwabe, and Yang.