.\"-
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.Dd May 15, 2022
.Dt CRYB_MD5 3
.Os
.Sh NAME
.Nm cryb_md5_init ,
.Nm cryb_md5_update ,
.Nm cryb_md5_final ,
.Nm cryb_md5_complete
.Nd Message-Digest Algorithm 2
.Sh LIBRARY
.Lb libcryb-digest
.Sh SYNOPSIS
.In stddef.h
.In stdint.h
.In cryb/md5.h
.Ft void
.Fn cryb_md5_init "cryb_md5_ctx *context"
.Ft void
.Fn cryb_md5_update "cryb_md5_ctx *context" "const void *data" "size_t len"
.Ft void
.Fn cryb_md5_final "cryb_md5_ctx *context" "uint8_t *digest"
.Ft void
.Fn cryb_md5_complete "const void *data" "size_t len" "uint8_t *digest"
.Sh DESCRIPTION
The
.Nm cryb_md5
family of functions implements the MD5 message digest algorithm as
described in RFC 1321.
.Pp
The
.Fn cryb_md5_init
function initializes the context structure pointed to by
.Va context .
It is the caller's responsibility to allocate this structure.
.Pp
The
.Fn cryb_md5_update
function hashes the next
.Va len
bytes of data pointed to by the
.Va data
pointer into the given hash context.
.Pp
The
.Fn cryb_md5_final
function finalizes the computation and writes the resulting message
digest to the caller-provided buffer pointed to by
.Va digest ,
which must be at least
.Dv MD5_DIGEST_LEN
bytes long.
It is the caller's responsibility to dispose of the context structure
after calling
.Fn cryb_md5_final .
.Pp
The
.Fn cryb_md5_complete
function is a shortcut to calling
.Fn cryb_md5_init ,
.Fn cryb_md5_update ,
and
.Fn cryb_md5_final
when the entire message is available up front in a single contiguous
buffer.
.Sh IMPLEMENTATION NOTES
The
.In cryb/md5.h
header provides macros which allows these functions and the context
type to be referred to without their
.Dq Li cryb_
prefix.
.Pp
The MD5 message digest algorithm has been proven to be vulnerable to
collision attacks and should not be used for cryptographic purposes.
.Sh SEE ALSO
.Xr cryb_digest 3 ,
.Xr cryb_md2 3 ,
.Xr cryb_md4 3
.Sh REFERENCES
.Rs
.%A Rivest, Ronald
.%T The MD5 Message-Digest Algorithm
.%D April 1992
.%O RFC 1321
.%U https://datatracker.ietf.org/doc/html/rfc1321
.Re
.Rs
.%A Turner, Sean
.%A Chen, Lily
.%T Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms
.%D March 2011
.%O RFC 6151
.%U https://datatracker.ietf.org/doc/html/rfc6151
.Re
.Sh AUTHORS
These functions and this manual page were written by
.An Dag-Erling Sm\(/orgrav Aq Mt des@des.no .