---
name: "mdc2"
section: "3ssl"
platform: "linux"
package: "libssl-doc"
version: "1.0.1t-1+deb8u8"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/mdc2/3ssl"
---

# mdc2(3ssl)

MDC2 hash function

## NAME

MDC2, MDC2\_Init, MDC2\_Update, MDC2\_Final - MDC2 hash function

## SYNOPSIS

```
 #include <openssl/mdc2.h>
 unsigned char *MDC2(const unsigned char *d, unsigned long n,
                  unsigned char *md);
 int MDC2_Init(MDC2_CTX *c);
 int MDC2_Update(MDC2_CTX *c, const unsigned char *data,
                  unsigned long len);
 int MDC2_Final(unsigned char *md, MDC2_CTX *c);
```

## DESCRIPTION

MDC2 is a method to construct hash functions with 128 bit output from block ciphers.  These functions are an implementation of MDC2 with DES.

*MDC2()* computes the MDC2 message digest of the **n** bytes at **d** and places it in **md** (which must have space for MDC2\_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:

*MDC2\_Init()* initializes a **MDC2\_CTX** structure.

*MDC2\_Update()* can be called repeatedly with chunks of the message to be hashed (**len** bytes at **data**).

*MDC2\_Final()* places the message digest in **md**, which must have space for MDC2\_DIGEST\_LENGTH == 16 bytes of output, and erases the **MDC2\_CTX**.

Applications should use the higher level functions *EVP\_DigestInit*(3) etc. instead of calling the hash functions directly.

## RETURN VALUES

*MDC2()* returns a pointer to the hash value.

*MDC2\_Init()*, *MDC2\_Update()* and *MDC2\_Final()* return 1 for success, 0 otherwise.

## CONFORMING TO

ISO/IEC 10118-2, with DES

## SEE ALSO

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

## HISTORY

*MDC2()*, *MDC2\_Init()*, *MDC2\_Update()* and *MDC2\_Final()* are available since SSLeay 0.8.