---
name: "md5"
section: "3ssl"
platform: "linux"
package: "libssl-doc"
version: "1.0.1t-1+deb8u8"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/md5/3ssl"
---

# md5(3ssl)

MD2, MD4, and MD5 hash functions

## 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*(3) 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*(3)](/sha/3.md), [*ripemd*(3)](/ripemd/3.md), *EVP\_DigestInit*(3)

## 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.