- NAME
- SYNOPSIS
- DESCRIPTION
- NOTE
- RETURN VALUES
- CONFORMING TO
- SEE ALSO
- HISTORY

# NAME

MD2, MD4, MD5, MD2_Init, MD2_Update, MD2_Final, MD4_Init, MD4_Update, MD4_Final, MD5_Init, MD5_Update, MD5_Final - MD2, MD4, and MD5 hash functions

# SYNOPSIS

     #include <openssl/md2.h>

     unsigned char *MD2(const unsigned char *d, unsigned long n,
                      unsigned char *md);

     int MD2_Init(MD2_CTX *c);
     int MD2_Update(MD2_CTX *c, const unsigned char *data,
                      unsigned long len);
     int MD2_Final(unsigned char *md, MD2_CTX *c);

     #include <openssl/md4.h>

     unsigned char *MD4(const unsigned char *d, unsigned long n,
                      unsigned char *md);

     int MD4_Init(MD4_CTX *c);
     int MD4_Update(MD4_CTX *c, const void *data,
                      unsigned long len);
     int MD4_Final(unsigned char *md, MD4_CTX *c);

     #include <openssl/md5.h>

     unsigned char *MD5(const unsigned char *d, unsigned long n,
                      unsigned char *md);

     int MD5_Init(MD5_CTX *c);
     int MD5_Update(MD5_CTX *c, const void *data,
                      unsigned long len);
     int MD5_Final(unsigned char *md, MD5_CTX *c);

# DESCRIPTION

MD2, MD4, and MD5 are cryptographic hash functions with a 128 bit output.

MD2(), MD4(), and `MD5()` compute the MD2, MD4, and MD5 message digest of the n bytes at d and place it in md (which must have space for MD2_DIGEST_LENGTH == MD4_DIGEST_LENGTH == MD5_DIGEST_LENGTH == 16 bytes of output). If md is NULL, the digest is placed in a static array.

The following functions may be used if the message is not completely stored in memory:

`MD2_Init()` initializes a MD2_CTX structure.

`MD2_Update()` can be called repeatedly with chunks of the message to be hashed (len bytes at data).

`MD2_Final()` places the message digest in md, which must have space for MD2_DIGEST_LENGTH == 16 bytes of output, and erases the MD2_CTX.

MD4_Init(), MD4_Update(), MD4_Final(), MD5_Init(), MD5_Update(), and `MD5_Final()` are analogous using an MD4_CTX and MD5_CTX structure.

Applications should use the higher level functions EVP_DigestInit etc. instead of calling the hash functions directly.

# NOTE

MD2, MD4, and MD5 are recommended only for compatibility with existing applications. In new applications, SHA-1 or RIPEMD-160 should be preferred.

# RETURN VALUES

MD2(), MD4(), and `MD5()` return pointers to the hash value.

MD2_Init(), MD2_Update(), MD2_Final(), MD4_Init(), MD4_Update(), MD4_Final(), MD5_Init(), MD5_Update(), and `MD5_Final()` return 1 for success, 0 otherwise.

# CONFORMING TO

RFC 1319, RFC 1320, RFC 1321

# SEE ALSO

sha, ripemd, EVP_DigestInit

# HISTORY

MD2(), MD2_Init(), `MD2_Update()` MD2_Final(), MD5(), MD5_Init(), `MD5_Update()` and `MD5_Final()` are available in all versions of SSLeay and OpenSSL.

MD4(), MD4_Init(), and `MD4_Update()` are available in OpenSSL 0.9.6 and above.