RSA_sign, RSA_verify - RSA signatures

```
#include <openssl/rsa.h>
int RSA_sign(int type, const unsigned char *m, unsigned int m_len,
unsigned char *sigret, unsigned int *siglen, RSA *rsa);
int RSA_verify(int type, const unsigned char *m, unsigned int m_len,
unsigned char *sigbuf, unsigned int siglen, RSA *rsa);
```

RSA_sign() signs the message digest **m** of size **m_len** using the private key **rsa** as specified in PKCS #1 v2.0. It stores the signature in **sigret** and the signature size in **siglen**. **sigret** must point to RSA_size(**rsa**) bytes of memory. Note that PKCS #1 adds meta-data, placing limits on the size of the key that can be used. See RSA_private_encrypt for lower-level operations.

**type** denotes the message digest algorithm that was used to generate **m**. It usually is one of **NID_sha1**, **NID_ripemd160** and **NID_md5**; see objects for details. If **type** is **NID_md5_sha1**, an SSL signature (MD5 and SHA1 message digests with PKCS #1 padding and no algorithm identifier) is created.

RSA_verify() verifies that the signature **sigbuf** of size **siglen** matches a given message digest **m** of size **m_len**. **type** denotes the message digest algorithm that was used to generate the signature. **rsa** is the signer's public key.

RSA_sign() returns 1 on success, 0 otherwise. RSA_verify() returns 1 on successful verification, 0 otherwise.

The error codes can be obtained by ERR_get_error.

Certain signatures with an improper algorithm identifier are accepted for compatibility with SSLeay 0.4.5 :-)

SSL, PKCS #1 v2.0

ERR_get_error, objects, rsa, RSA_private_encrypt, RSA_public_decrypt

RSA_sign() and RSA_verify() are available in all versions of SSLeay and OpenSSL.