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✏️ Editing: SHA256.3

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.\" ========================================================================
.\"
.IX Title "SHA256_INIT 3"
.TH SHA256_INIT 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
SHA1, SHA1_Init, SHA1_Update, SHA1_Final, SHA224, SHA224_Init, SHA224_Update, SHA224_Final, SHA256, SHA256_Init, SHA256_Update, SHA256_Final, SHA384, SHA384_Init, SHA384_Update, SHA384_Final, SHA512, SHA512_Init, SHA512_Update, SHA512_Final \- Secure Hash Algorithm
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/sha.h>
\&
\& int SHA1_Init(SHA_CTX *c);
\& int SHA1_Update(SHA_CTX *c, const void *data, size_t len);
\& int SHA1_Final(unsigned char *md, SHA_CTX *c);
\& unsigned char *SHA1(const unsigned char *d, size_t n,
\&                     unsigned char *md);
\&
\& int SHA224_Init(SHA256_CTX *c);
\& int SHA224_Update(SHA256_CTX *c, const void *data, size_t len);
\& int SHA224_Final(unsigned char *md, SHA256_CTX *c);
\& unsigned char *SHA224(const unsigned char *d, size_t n,
\&                       unsigned char *md);
\&
\& int SHA256_Init(SHA256_CTX *c);
\& int SHA256_Update(SHA256_CTX *c, const void *data, size_t len);
\& int SHA256_Final(unsigned char *md, SHA256_CTX *c);
\& unsigned char *SHA256(const unsigned char *d, size_t n,
\&                       unsigned char *md);
\&
\& int SHA384_Init(SHA512_CTX *c);
\& int SHA384_Update(SHA512_CTX *c, const void *data, size_t len);
\& int SHA384_Final(unsigned char *md, SHA512_CTX *c);
\& unsigned char *SHA384(const unsigned char *d, size_t n,
\&                       unsigned char *md);
\&
\& int SHA512_Init(SHA512_CTX *c);
\& int SHA512_Update(SHA512_CTX *c, const void *data, size_t len);
\& int SHA512_Final(unsigned char *md, SHA512_CTX *c);
\& unsigned char *SHA512(const unsigned char *d, size_t n,
\&                       unsigned char *md);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Applications should use the higher level functions
\&\fBEVP_DigestInit\fR\|(3) etc. instead of calling the hash
functions directly.
.PP
\&\s-1SHA\-1\s0 (Secure Hash Algorithm) is a cryptographic hash function with a
160 bit output.
.PP
\&\s-1\fBSHA1\s0()\fR computes the \s-1SHA\-1\s0 message digest of the \fBn\fR
bytes at \fBd\fR and places it in \fBmd\fR (which must have space for
\&\s-1SHA_DIGEST_LENGTH\s0 == 20 bytes of output). If \fBmd\fR is \s-1NULL,\s0 the digest
is placed in a static array. Note: setting \fBmd\fR to \s-1NULL\s0 is \fBnot thread safe\fR.
.PP
The following functions may be used if the message is not completely
stored in memory:
.PP
\&\fBSHA1_Init()\fR initializes a \fB\s-1SHA_CTX\s0\fR structure.
.PP
\&\fBSHA1_Update()\fR can be called repeatedly with chunks of the message to
be hashed (\fBlen\fR bytes at \fBdata\fR).
.PP
\&\fBSHA1_Final()\fR places the message digest in \fBmd\fR, which must have space
for \s-1SHA_DIGEST_LENGTH\s0 == 20 bytes of output, and erases the \fB\s-1SHA_CTX\s0\fR.
.PP
The \s-1SHA224, SHA256, SHA384\s0 and \s-1SHA512\s0 families of functions operate in the
same way as for the \s-1SHA1\s0 functions. Note that \s-1SHA224\s0 and \s-1SHA256\s0 use a
\&\fB\s-1SHA256_CTX\s0\fR object instead of \fB\s-1SHA_CTX\s0\fR. \s-1SHA384\s0 and \s-1SHA512\s0 use \fB\s-1SHA512_CTX\s0\fR.
The buffer \fBmd\fR must have space for the output from the \s-1SHA\s0 variant being used
(defined by \s-1SHA224_DIGEST_LENGTH, SHA256_DIGEST_LENGTH, SHA384_DIGEST_LENGTH\s0 and
\&\s-1SHA512_DIGEST_LENGTH\s0). Also note that, as for the \s-1\fBSHA1\s0()\fR function above, the
\&\s-1\fBSHA224\s0()\fR, \s-1\fBSHA256\s0()\fR, \s-1\fBSHA384\s0()\fR and \s-1\fBSHA512\s0()\fR functions are not thread safe if
\&\fBmd\fR is \s-1NULL.\s0
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\s-1\fBSHA1\s0()\fR, \s-1\fBSHA224\s0()\fR, \s-1\fBSHA256\s0()\fR, \s-1\fBSHA384\s0()\fR and \s-1\fBSHA512\s0()\fR return a pointer to the hash
value.
.PP
\&\fBSHA1_Init()\fR, \fBSHA1_Update()\fR and \fBSHA1_Final()\fR and equivalent \s-1SHA224, SHA256,
SHA384\s0 and \s-1SHA512\s0 functions return 1 for success, 0 otherwise.
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1US\s0 Federal Information Processing Standard \s-1FIPS PUB 180\-4\s0 (Secure Hash
Standard),
\&\s-1ANSI X9.30\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_DigestInit\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (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
<https://www.openssl.org/source/license.html>.

MR SKB