.Dd $Mdocdate: November 3 2016 $
.Dt MD5 3
.Os
.Sh NAME
.Nm MD2 ,
.Nm MD4 ,
.Nm MD5 ,
.Nm MD2_Init ,
.Nm MD2_Update ,
.Nm MD2_Final ,
.Nm MD4_Init ,
.Nm MD4_Update ,
.Nm MD4_Final ,
.Nm MD5_Init ,
.Nm MD5_Update ,
.Nm MD5_Final
.Nd MD2, MD4, and MD5 hash functions
.Sh SYNOPSIS
.In openssl/md2.h
.Ft unsigned char *
.Fo MD2
.Fa "const unsigned char *d"
.Fa "unsigned long n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo MD2_Init
.Fa "MD2_CTX *c"
.Fc
.Ft int
.Fo MD2_Update
.Fa "MD2_CTX *c"
.Fa "const unsigned char *data"
.Fa "unsigned long len"
.Fc
.Ft int
.Fo MD2_Final
.Fa "unsigned char *md"
.Fa "MD2_CTX *c"
.Fc
.In openssl/md4.h
.Ft unsigned char *
.Fo MD4
.Fa "const unsigned char *d"
.Fa "unsigned long n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo MD4_Init
.Fa "MD4_CTX *c"
.Fc
.Ft int
.Fo MD4_Update
.Fa "MD4_CTX *c"
.Fa "const void *data"
.Fa "unsigned long len"
.Fc
.Ft int
.Fo MD4_Final
.Fa "unsigned char *md"
.Fa "MD4_CTX *c"
.Fc
.In openssl/md5.h
.Ft unsigned char *
.Fo MD5
.Fa "const unsigned char *d"
.Fa "unsigned long n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo MD5_Init
.Fa "MD5_CTX *c"
.Fc
.Ft int
.Fo MD5_Update
.Fa "MD5_CTX *c"
.Fa "const void *data"
.Fa "unsigned long len"
.Fc
.Ft int
.Fo MD5_Final
.Fa "unsigned char *md"
.Fa "MD5_CTX *c"
.Fc
.Sh DESCRIPTION
MD2, MD4, and MD5 are cryptographic hash functions with a 128 bit
output.
.Pp
.Fn MD2 ,
.Fn MD4 ,
and
.Fn MD5
compute the MD2, MD4, and MD5 message digest of the
.Fa n
bytes at
.Fa d
and place it in
.Fa md ,
which must have space for
.Dv MD2_DIGEST_LENGTH No ==
.Dv MD4_DIGEST_LENGTH No ==
.Dv MD5_DIGEST_LENGTH No == 16
bytes of output.
If
.Fa md
is
.Dv NULL ,
the digest is placed in a static array.
.Pp
The following functions may be used if the message is not completely
stored in memory:
.Pp
.Fn MD2_Init
initializes a
.Vt MD2_CTX
structure.
.Pp
.Fn MD2_Update
can be called repeatedly with chunks of the message to be hashed
.Pq Fa len No bytes at Fa data .
.Pp
.Fn MD2_Final
places the message digest in
.Fa md ,
which must have space for
.Dv MD2_DIGEST_LENGTH No == 16
bytes of output, and erases the
.Vt MD2_CTX .
.Pp
.Fn MD4_Init ,
.Fn MD4_Update ,
.Fn MD4_Final ,
.Fn MD5_Init ,
.Fn MD5_Update ,
and
.Fn MD5_Final
are analogous using an
.Vt MD4_CTX
and
.Vt MD5_CTX
structure.
.Pp
Applications should use the higher level functions
.Xr EVP_DigestInit 3
etc. instead of calling these hash functions directly.
.Sh RETURN VALUES
.Fn MD2 ,
.Fn MD4 ,
and
.Fn MD5
return pointers to the hash value.
.Pp
.Fn MD2_Init ,
.Fn MD2_Update ,
.Fn MD2_Final ,
.Fn MD4_Init ,
.Fn MD4_Update ,
.Fn MD4_Final ,
.Fn MD5_Init ,
.Fn MD5_Update ,
and
.Fn MD5_Final
return 1 for success or 0 otherwise.
.Sh SEE ALSO
.Xr EVP_DigestInit 3
.Sh STANDARDS
RFC 1319, RFC 1320, RFC 1321
.Sh HISTORY
.Fn MD2 ,
.Fn MD2_Init ,
.Fn MD2_Update ,
.Fn MD2_Final ,
.Fn MD5 ,
.Fn MD5_Init ,
.Fn MD5_Update ,
and
.Fn MD5_Final
are available in all versions of SSLeay and OpenSSL.
.Pp
.Fn MD4 ,
.Fn MD4_Init ,
and
.Fn MD4_Update
are available in OpenSSL 0.9.6 and above.