'\" te
.\" Copyright (c) 2007, 2012, Oracle and/or its affiliates. All rights reserved.
.TH sha1 3EXT "20 Feb 2012" "SunOS 5.11" "Extended Library Functions"
.SH NAME
sha1, SHA1Init, SHA1Update, SHA1Final \- SHA1 digest functions
.SH SYNOPSIS
.LP
.nf
\fBcc\fR [ \fIflag\fR ... ] \fIfile\fR ... \fB-lmd\fR [ \fIlibrary\fR ... ]
#include <sha1.h>

\fBvoid\fR \fBSHA1Init\fR(\fBSHA1_CTX *\fR\fIcontext\fR);
.fi

.LP
.nf
\fBvoid\fR \fBSHA1Update\fR(\fBSHA1_CTX *\fR\fIcontext\fR, \fBunsigned char *\fR\fIinput\fR,
     \fBunsigned int\fR \fIinlen\fR);
.fi

.LP
.nf
\fBvoid\fR \fBSHA1Final\fR(\fBunsigned char *\fR\fIoutput\fR, \fBSHA1_CTX *\fR\fIcontext\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBSHA1\fR functions implement the \fBSHA1\fR message-digest algorithm. The algorithm takes as input a message of arbitrary length and produces a 160-bit "fingerprint" or "message digest" as output. The \fBSHA1\fR message-digest algorithm is intended for digital signature applications in which large files are "compressed" in a secure manner before being encrypted with a private (secret) key under a public-key cryptosystem such as RSA.
.sp
.ne 2
.mk
.na
\fB\fBSHA1Init()\fR, \fBSHA1Update()\fR, \fBSHA1Final()\fR\fR
.ad
.sp .6
.RS 4n
The \fBSHA1Init()\fR, \fBSHA1Update()\fR, and \fBSHA1Final()\fR functions allow a \fBSHA1\fR digest to be computed over multiple message blocks. Between blocks, the state of the \fBSHA1\fR computation is held in an \fBSHA1\fR context structure allocated by the caller. A complete digest computation consists of calls to \fBSHA1\fR functions in the following order: one call to \fBSHA1Init()\fR, one or more calls to \fBSHA1Update()\fR, and one call to \fBSHA1Final()\fR.
.sp
The \fBSHA1Init()\fR function initializes the \fBSHA1\fR context structure pointed to by \fIcontext\fR.
.sp
The \fBSHA1Update()\fR function computes a partial \fBSHA1\fR digest on the \fIinlen\fR-byte message block pointed to by \fIinput\fR, and updates the \fBSHA1\fR context structure pointed to by \fIcontext\fR accordingly.
.sp
The \fBSHA1Final()\fR function generates the final \fBSHA1\fR digest, using the \fBSHA1\fR context structure pointed to by \fIcontext\fR. The 16-bit \fBSHA1\fR digest is written to output. After a call to \fBSHA1Final()\fR, the state of the context structure is undefined. It must be reinitialized with \fBSHA1Init()\fR before it can be used again.
.RE

.SH SECURITY
.sp
.LP
The \fBSHA1\fR algorithm is also believed to have some weaknesses. Migration to one of the \fBSHA2\fR algorithms-including \fBSHA224\fR, \fBSHA256\fR, \fBSHA386\fR or \fBSHA512\fR-is highly recommended when compatibility with data formats and on wire protocols is permitted.
.SH RETURN VALUES
.sp
.LP
These functions do not return a value.
.SH EXAMPLES
.LP
\fBExample 1 \fRAuthenticate a message found in multiple buffers
.sp
.LP
The following is a sample function that authenticates a message found in multiple buffers. The calling function provides an authentication buffer to contain the result of the \fBSHA1\fR digest.

.sp
.in +2
.nf
#include <sys/types.h>
#include <sys/uio.h>
#include <sha1.h>

int
AuthenticateMsg(unsigned char *auth_buffer, struct iovec 
                *messageIov, unsigned int num_buffers)
{
    SHA1_CTX sha1_context;
    unsigned int i;

    SHA1Init(&sha1_context);

    for(i=0; i<num_buffers; i++)
    {
         SHA1Update(&sha1_context, messageIov->iov_base,
                   messageIov->iov_len);
         messageIov += sizeof(struct iovec);
    }

    SHA1Final(auth_buffer, &sha1_context);

    return 0;
}
.fi
.in -2

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBsha2\fR(3EXT), \fBlibmd\fR(3LIB)
.sp
.LP
RFC 1374