1EVP_SignInit(3) OpenSSL EVP_SignInit(3)
2
6 EVP_SignInit, EVP_SignInit_ex, EVP_SignUpdate, EVP_SignFinal - EVP
7 signing functions
8
10 #include <openssl/evp.h>
11 int EVP_SignInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
13 int EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
14 int EVP_SignFinal(EVP_MD_CTX *ctx,unsigned char *sig,unsigned int *s, EVP_PKEY *pkey);
15 void EVP_SignInit(EVP_MD_CTX *ctx, const EVP_MD *type);
17 int EVP_PKEY_size(EVP_PKEY *pkey);
19
21 The EVP signature routines are a high level interface to digital
22 signatures.
23 EVP_SignInit_ex() sets up signing context ctx to use digest type from
25 ENGINE impl. ctx must be initialized with EVP_MD_CTX_init() before
26 calling this function.
27 EVP_SignUpdate() hashes cnt bytes of data at d into the signature
29 context ctx. This function can be called several times on the same ctx
30 to include additional data.
31 EVP_SignFinal() signs the data in ctx using the private key pkey and
33 places the signature in sig. sig must be at least EVP_PKEY_size(pkey)
34 bytes in size. s is an OUT paramter, and not used as an IN parameter.
35 The number of bytes of data written (i.e. the length of the signature)
36 will be written to the integer at s, at most EVP_PKEY_size(pkey) bytes
37 will be written.
38 EVP_SignInit() initializes a signing context ctx to use the default
40 implementation of digest type.
41 EVP_PKEY_size() returns the maximum size of a signature in bytes. The
43 actual signature returned by EVP_SignFinal() may be smaller.
44
46 EVP_SignInit_ex(), EVP_SignUpdate() and EVP_SignFinal() return 1 for
47 success and 0 for failure.
48 EVP_PKEY_size() returns the maximum size of a signature in bytes.
50 The error codes can be obtained by ERR_get_error(3).
52
54 The EVP interface to digital signatures should almost always be used in
55 preference to the low level interfaces. This is because the code then
56 becomes transparent to the algorithm used and much more flexible.
57 Due to the link between message digests and public key algorithms the
59 correct digest algorithm must be used with the correct public key type.
60 A list of algorithms and associated public key algorithms appears in
61 EVP_DigestInit(3).
62 When signing with DSA private keys the random number generator must be
64 seeded or the operation will fail. The random number generator does not
65 need to be seeded for RSA signatures.
66 The call to EVP_SignFinal() internally finalizes a copy of the digest
68 context. This means that calls to EVP_SignUpdate() and EVP_SignFinal()
69 can be called later to digest and sign additional data.
70 Since only a copy of the digest context is ever finalized the context
72 must be cleaned up after use by calling EVP_MD_CTX_cleanup() or a
73 memory leak will occur.
74
76 Older versions of this documentation wrongly stated that calls to
77 EVP_SignUpdate() could not be made after calling EVP_SignFinal().
78 Since the private key is passed in the call to EVP_SignFinal() any
80 error relating to the private key (for example an unsuitable key and
81 digest combination) will not be indicated until after potentially large
82 amounts of data have been passed through EVP_SignUpdate().
83 It is not possible to change the signing parameters using these
85 function.
86 The previous two bugs are fixed in the newer EVP_SignDigest*()
88 function.
89
91 EVP_VerifyInit(3), EVP_DigestInit(3), err(3), evp(3), hmac(3), md2(3),
92 md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)
93
95 EVP_SignInit(), EVP_SignUpdate() and EVP_SignFinal() are available in
96 all versions of SSLeay and OpenSSL.
97 EVP_SignInit_ex() was added in OpenSSL 0.9.7.
991.0.2o 2020-08-01 EVP_SignInit(3)