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

# sha(3ssl)

Secure Hash Algorithm

## NAME

SHA1, SHA1\_Init, SHA1\_Update, SHA1\_Final - Secure Hash Algorithm

## SYNOPSIS

```
 #include <openssl/sha.h>
 unsigned char *SHA1(const unsigned char *d, unsigned long n,
                  unsigned char *md);
 int SHA1_Init(SHA_CTX *c);
 int SHA1_Update(SHA_CTX *c, const void *data,
                  unsigned long len);
 int SHA1_Final(unsigned char *md, SHA_CTX *c);
```

## DESCRIPTION

SHA-1 (Secure Hash Algorithm) is a cryptographic hash function with a 160 bit output.

*SHA1()* computes the SHA-1 message digest of the **n** bytes at **d** and places it in **md** (which must have space for SHA\_DIGEST\_LENGTH == 20 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:

*SHA1\_Init()* initializes a **SHA\_CTX** structure.

*SHA1\_Update()* can be called repeatedly with chunks of the message to be hashed (**len** bytes at **data**).

*SHA1\_Final()* places the message digest in **md**, which must have space for SHA\_DIGEST\_LENGTH == 20 bytes of output, and erases the **SHA\_CTX**.

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

The predecessor of SHA-1, SHA, is also implemented, but it should be used only when backward compatibility is required.

## RETURN VALUES

*SHA1()* returns a pointer to the hash value.

*SHA1\_Init()*, *SHA1\_Update()* and *SHA1\_Final()* return 1 for success, 0 otherwise.

## CONFORMING TO

SHA: US Federal Information Processing Standard FIPS PUB 180 (Secure Hash Standard), SHA-1: US Federal Information Processing Standard FIPS PUB 180-1 (Secure Hash Standard), ANSI X9.30

## SEE ALSO

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

## HISTORY

*SHA1()*, *SHA1\_Init()*, *SHA1\_Update()* and *SHA1\_Final()* are available in all versions of SSLeay and OpenSSL.