=pod
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=head1 NAME
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SHA1, SHA1_Init, SHA1_Update, SHA1_Final - Secure Hash Algorithm
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=head1 SYNOPSIS
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#include <openssl/sha.h>
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unsigned char *SHA1(const unsigned char *d, unsigned long n,
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unsigned char *md);
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int SHA1_Init(SHA_CTX *c);
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int SHA1_Update(SHA_CTX *c, const void *data,
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unsigned long len);
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int SHA1_Final(unsigned char *md, SHA_CTX *c);
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=head1 DESCRIPTION
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SHA-1 (Secure Hash Algorithm) is a cryptographic hash function with a
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160 bit output.
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SHA1() computes the SHA-1 message digest of the B<n>
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bytes at B<d> and places it in B<md> (which must have space for
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SHA_DIGEST_LENGTH == 20 bytes of output). If B<md> is NULL, the digest
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is placed in a static array.
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The following functions may be used if the message is not completely
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stored in memory:
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SHA1_Init() initializes a B<SHA_CTX> structure.
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SHA1_Update() can be called repeatedly with chunks of the message to
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be hashed (B<len> bytes at B<data>).
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SHA1_Final() places the message digest in B<md>, which must have space
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for SHA_DIGEST_LENGTH == 20 bytes of output, and erases the B<SHA_CTX>.
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Applications should use the higher level functions
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L<EVP_DigestInit(3)|EVP_DigestInit(3)>
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etc. instead of calling the hash functions directly.
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The predecessor of SHA-1, SHA, is also implemented, but it should be
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used only when backward compatibility is required.
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=head1 RETURN VALUES
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SHA1() returns a pointer to the hash value.
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SHA1_Init(), SHA1_Update() and SHA1_Final() return 1 for success, 0 otherwise.
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=head1 CONFORMING TO
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SHA: US Federal Information Processing Standard FIPS PUB 180 (Secure Hash
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Standard),
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SHA-1: US Federal Information Processing Standard FIPS PUB 180-1 (Secure Hash
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Standard),
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ANSI X9.30
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=head1 SEE ALSO
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L<ripemd(3)|ripemd(3)>, L<hmac(3)|hmac(3)>, L<EVP_DigestInit(3)|EVP_DigestInit(3)>
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=head1 HISTORY
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SHA1(), SHA1_Init(), SHA1_Update() and SHA1_Final() are available in all
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versions of SSLeay and OpenSSL.
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=cut
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