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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" EVP_SIGNATURE\-ED25519, EVP_SIGNATURE\-ED448, Ed25519, Ed448 \&\- EVP_PKEY Ed25519 and Ed448 support .SH "DESCRIPTION" .IX Header "DESCRIPTION" The \fBEd25519\fR and \fBEd448\fR \s-1EVP_PKEY\s0 implementation supports key generation, one-shot digest-sign and digest-verify using the EdDSA signature scheme described in \s-1RFC 8032.\s0 It has associated private and public key formats compatible with \s-1RFC 8410.\s0 .SS "EdDSA Instances" .IX Subsection "EdDSA Instances" \&\s-1RFC 8032\s0 describes five EdDSA instances: Ed25519, Ed25519ctx, Ed25519ph, Ed448, Ed448ph. .PP The instances Ed25519, Ed25519ctx, Ed448 are referred to as \fBPureEdDSA\fR schemes. For these three instances, the sign and verify procedures require access to the complete message (not a digest of the message). .PP The instances Ed25519ph, Ed448ph are referred to as \fBHashEdDSA\fR 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 \s-1SHA512. \s0 For Ed448ph, the hash function is \s-1SHAKE256\s0 with an output length of 512 bits. .PP The instances Ed25519ctx, Ed25519ph, Ed448, Ed448ph accept an optional \&\fBcontext-string\fR 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. .SS "\s-1ED25519\s0 and \s-1ED448\s0 Signature Parameters" .IX Subsection "ED25519 and ED448 Signature Parameters" Two parameters can be set during signing or verification: the EdDSA \&\fBinstance name\fR and the \fBcontext-string value\fR. They can be set by passing an \s-1OSSL_PARAM\s0 array to \fIEVP_DigestSignInit_ex()\fR. .IP "\(bu" 4 \&\*(L"instance\*(R" (\fB\s-1OSSL_SIGNATURE_PARAM_INSTANCE\s0\fR) .Sp One of the five strings \*(L"Ed25519\*(R", \*(L"Ed25519ctx\*(R", \*(L"Ed25519ph\*(R", \*(L"Ed448\*(R", \*(L"Ed448ph\*(R". .Sp \&\*(L"Ed25519\*(R", \*(L"Ed25519ctx\*(R", \*(L"Ed25519ph\*(R" are valid only for an Ed25519 \s-1EVP_PKEY.\s0 .Sp \&\*(L"Ed448\*(R", \*(L"Ed448ph\*(R" are valid only for an Ed448 \s-1EVP_PKEY.\s0 .IP "\(bu" 4 \&\*(L"context-string\*(R" (\fB\s-1OSSL_SIGNATURE_PARAM_CONTEXT_STRING\s0\fR) .Sp A string of octets with length at most 255. .PP Both of these parameters are optional. .PP If the instance name is not specified, then the default \*(L"Ed25519\*(R" or \&\*(L"Ed448\*(R" is used. .PP If a context-string is not specified, then an empty context-string is used. .PP Note that a message digest name must \fB\s-1NOT\s0\fR be specified when signing or verifying. .PP See \s-1\fIEVP_PKEY\-X25519\s0\fR\|(7) for information related to \fBX25519\fR and \fBX448\fR keys. .PP The following signature parameters can be retrieved using \&\fIEVP_PKEY_CTX_get_params()\fR. .IP "\(bu" 4 \&\*(L"algorithm-id\*(R" (\fB\s-1OSSL_SIGNATURE_PARAM_ALGORITHM_ID\s0\fR) .IP "\(bu" 4 \&\*(L"instance\*(R" (\fB\s-1OSSL_SIGNATURE_PARAM_INSTANCE\s0\fR) .IP "\(bu" 4 \&\*(L"context-string\*(R" (\fB\s-1OSSL_SIGNATURE_PARAM_CONTEXT_STRING\s0\fR) .PP The parameters are described in \fIprovider\-signature\fR\|(7). .SH "NOTES" .IX Header "NOTES" The PureEdDSA instances do not support the streaming mechanism of other signature algorithms using, for example, \fIEVP_DigestUpdate()\fR. The message to sign or verify must be passed using the one-shot \&\fIEVP_DigestSign()\fR and \fIEVP_DigestVerify()\fR functions. .PP The HashEdDSA instances do not yet support the streaming mechanisms (so the one-shot functions must be used with HashEdDSA as well). .PP When calling \fIEVP_DigestSignInit()\fR or \fIEVP_DigestVerifyInit()\fR, the digest \fItype\fR parameter \fB\s-1MUST\s0\fR be set to \s-1NULL.\s0 .PP Applications wishing to sign certificates (or other structures such as CRLs or certificate requests) using Ed25519 or Ed448 can either use \fIX509_sign()\fR or \fIX509_sign_ctx()\fR in the usual way. .PP Ed25519 or Ed448 private keys can be set directly using \&\fIEVP_PKEY_new_raw_private_key\fR\|(3) or loaded from a PKCS#8 private key file using \fIPEM_read_bio_PrivateKey\fR\|(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. .PP Ed25519 or Ed448 public keys can be set directly using \&\fIEVP_PKEY_new_raw_public_key\fR\|(3) or loaded from a SubjectPublicKeyInfo structure in a \s-1PEM\s0 file using \fIPEM_read_bio_PUBKEY\fR\|(3) (or similar function). .PP Ed25519 and Ed448 can be tested with the \fIopenssl\-speed\fR\|(1) application since version 1.1.1. Valid algorithm names are \fBed25519\fR, \fBed448\fR and \fBeddsa\fR. If \fBeddsa\fR is specified, then both Ed25519 and Ed448 are benchmarked. .SH "EXAMPLES" .IX Header "EXAMPLES" To sign a message using an \s-1ED25519 EVP_PKEY\s0 structure: .PP .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 .SH "SEE ALSO" .IX Header "SEE ALSO" \&\s-1\fIEVP_PKEY\-X25519\s0\fR\|(7) \&\fIprovider\-signature\fR\|(7), \&\fIEVP_DigestSignInit\fR\|(3), \&\fIEVP_DigestVerifyInit\fR\|(3), .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2017\-2023 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at .