5 EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal,
6 EVP_DigestSign - EVP signing functions
10 #include <openssl/evp.h>
12 int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
13 const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
14 int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
15 int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);
17 int EVP_DigestSign(EVP_MD_CTX *ctx, unsigned char *sigret,
18 size_t *siglen, const unsigned char *tbs,
23 The EVP signature routines are a high level interface to digital signatures.
25 EVP_DigestSignInit() sets up signing context B<ctx> to use digest B<type> from
26 ENGINE B<e> and private key B<pkey>. B<ctx> must be created with
27 EVP_MD_CTX_new() before calling this function. If B<pctx> is not NULL the
28 EVP_PKEY_CTX of the signing operation will be written to B<*pctx>: this can
29 be used to set alternative signing options. The digest B<type> may be NULL if
30 the signing algorithm supports it.
32 Only EVP_PKEY types that support signing can be used with these functions. This
33 includes MAC algorithms where the MAC generation is considered as a form of
34 "signing." Built-in EVP_PKEY types supported by these functions are CMAC,
35 Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448.
37 Not all digests can be used for all key types. The following combinations apply.
43 Supports SHA1, SHA224, SHA256, SHA384 and SHA512
47 Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3
49 =item RSA with no padding
51 Supports no digests (the digest B<type> must be NULL)
53 =item RSA with X931 padding
55 Supports SHA1, SHA256, SHA384 and SHA512
57 =item All other RSA padding types
59 Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
60 SHA3-224, SHA3-256, SHA3-384, SHA3-512
62 =item Ed25519 and Ed448
64 Support no digests (the digest B<type> must be NULL)
70 =item CMAC, Poly1305 and SipHash
72 Will ignore any digest provided.
76 If RSA-PSS is used and restrictions apply then the digest must match.
78 EVP_DigestSignUpdate() hashes B<cnt> bytes of data at B<d> into the
79 signature context B<ctx>. This function can be called several times on the
80 same B<ctx> to include additional data. This function is currently implemented
83 EVP_DigestSignFinal() signs the data in B<ctx> places the signature in B<sig>.
84 If B<sig> is B<NULL> then the maximum size of the output buffer is written to
85 the B<siglen> parameter. If B<sig> is not B<NULL> then before the call the
86 B<siglen> parameter should contain the length of the B<sig> buffer, if the
87 call is successful the signature is written to B<sig> and the amount of data
90 EVP_DigestSign() signs B<tbslen> bytes of data at B<tbs> and places the
91 signature in B<sig> and its length in B<siglen> in a similar way to
92 EVP_DigestSignFinal().
96 EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignaFinal() and
97 EVP_DigestSign() return 1 for success and 0 or a negative value for failure. In
98 particular a return value of -2 indicates the operation is not supported by the
101 The error codes can be obtained from L<ERR_get_error(3)>.
105 The B<EVP> interface to digital signatures should almost always be used in
106 preference to the low level interfaces. This is because the code then becomes
107 transparent to the algorithm used and much more flexible.
109 EVP_DigestSign() is a one shot operation which signs a single block of data
110 in one function. For algorithms that support streaming it is equivalent to
111 calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which
112 do not support streaming (e.g. PureEdDSA) it is the only way to sign data.
114 In previous versions of OpenSSL there was a link between message digest types
115 and public key algorithms. This meant that "clone" digests such as EVP_dss1()
116 needed to be used to sign using SHA1 and DSA. This is no longer necessary and
117 the use of clone digest is now discouraged.
119 For some key types and parameters the random number generator must be seeded
120 or the operation will fail.
122 The call to EVP_DigestSignFinal() internally finalizes a copy of the digest
123 context. This means that calls to EVP_DigestSignUpdate() and
124 EVP_DigestSignFinal() can be called later to digest and sign additional data.
126 Since only a copy of the digest context is ever finalized the context must
127 be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak
130 The use of EVP_PKEY_size() with these functions is discouraged because some
131 signature operations may have a signature length which depends on the
132 parameters set. As a result EVP_PKEY_size() would have to return a value
133 which indicates the maximum possible signature for any set of parameters.
137 L<EVP_DigestVerifyInit(3)>,
138 L<EVP_DigestInit(3)>,
139 L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
140 L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
141 L<SHA1(3)>, L<dgst(1)>
145 EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
146 were first added to OpenSSL 1.0.0.
150 Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved.
152 Licensed under the OpenSSL license (the "License"). You may not use
153 this file except in compliance with the License. You can obtain a copy
154 in the file LICENSE in the source distribution or at
155 L<https://www.openssl.org/source/license.html>.