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Title "EVP_SIGNATURE-ED25519 7ossl"
way too many mistakes in technical documents.
The instances Ed25519, Ed25519ctx, Ed448 are referred to as PureEdDSA schemes. For these three instances, the sign and verify procedures require access to the complete message (not a digest of the message).
The instances Ed25519ph, Ed448ph are referred to as HashEdDSA schemes. For these two instances, the sign and verify procedures do not require access to the complete message; they operate on a hash of the message. For Ed25519ph, the hash function is SHA512. For Ed448ph, the hash function is SHAKE256 with an output length of 512 bits.
The instances Ed25519ctx, Ed25519ph, Ed448, Ed448ph accept an optional \fBcontext-string as input to sign and verify operations (and for Ed25519ctx, the context-string must be nonempty). For the Ed25519 instance, a nonempty context-string is not permitted.
These instances can be specified as signature parameters when using \fBEVP_DigestSignInit\|(3) and EVP_DigestVerifyInit\|(3), see "ED25519 and ED448 Signature Parameters" below.
These instances are also explicitly fetchable as algorithms using \fBEVP_SIGNATURE_fetch\|(3), which can be used with \fBEVP_PKEY_sign_init_ex2\|(3), EVP_PKEY_verify_init_ex2\|(3), \fBEVP_PKEY_sign_message_init\|(3) and EVP_PKEY_verify_message_init\|(3).
Both of these parameters are optional.
When using EVP_DigestSignInit\|(3) or EVP_DigestVerifyInit\|(3), the signature algorithm is derived from the key type name. The key type name ("Ed25519" or "Ed448") is also the default for the instance, but this can be changed with the "instance" parameter.
Note that a message digest name must NOT be specified when signing or verifying.
When using EVP_PKEY_sign_init_ex2\|(3), EVP_PKEY_verify_init_ex2\|(3), \fBEVP_PKEY_sign_message_init\|(3) or EVP_PKEY_verify_message_init\|(3), the instance is the explicit signature algorithm name, and may not be changed (trying to give one with the "instance" parameter is therefore an error).
If a context-string is not specified, then an empty context-string is used.
See EVP_PKEY-X25519\|(7) for information related to X25519 and X448 keys.
The following signature parameters can be retrieved using \fBEVP_PKEY_CTX_get_params().
The parameters are described in provider-signature\|(7).
The HashEdDSA instances do not yet support the streaming mechanisms (so the one-shot functions must be used with HashEdDSA as well).
When calling EVP_DigestSignInit() or EVP_DigestVerifyInit(), the digest type parameter MUST be set to NULL.
Applications wishing to sign certificates (or other structures such as CRLs or certificate requests) using Ed25519 or Ed448 can either use X509_sign() or X509_sign_ctx() in the usual way.
Ed25519 or Ed448 private keys can be set directly using \fBEVP_PKEY_new_raw_private_key\|(3) or loaded from a PKCS#8 private key file using PEM_read_bio_PrivateKey\|(3) (or similar function). Completely new keys can also be generated (see the example below). Setting a private key also sets the associated public key.
Ed25519 or Ed448 public keys can be set directly using \fBEVP_PKEY_new_raw_public_key\|(3) or loaded from a SubjectPublicKeyInfo structure in a PEM file using PEM_read_bio_PUBKEY\|(3) (or similar function).
Ed25519 and Ed448 can be tested with the openssl-speed\|(1) application since version 1.1.1. Valid algorithm names are ed25519, ed448 and eddsa. If eddsa is specified, then both Ed25519 and Ed448 are benchmarked.
.Vb 5 void do_sign(EVP_PKEY *ed_key, unsigned char *msg, size_t msg_len) { size_t sig_len; unsigned char *sig = NULL; EVP_MD_CTX *md_ctx = EVP_MD_CTX_new(); \& const OSSL_PARAM params[] = { OSSL_PARAM_utf8_string ("instance", "Ed25519ctx", 10), OSSL_PARAM_octet_string("context-string", (unsigned char *)"A protocol defined context string", 33), OSSL_PARAM_END }; \& /* The input "params" is not needed if default options are acceptable. Use NULL in place of "params" in that case. */ EVP_DigestSignInit_ex(md_ctx, NULL, NULL, NULL, NULL, ed_key, params); /* Calculate the required size for the signature by passing a NULL buffer. */ EVP_DigestSign(md_ctx, NULL, &sig_len, msg, msg_len); sig = OPENSSL_zalloc(sig_len); \& EVP_DigestSign(md_ctx, sig, &sig_len, msg, msg_len); ... OPENSSL_free(sig); EVP_MD_CTX_free(md_ctx); } .Ve
Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.