libressl-EVP_VerifyInit3
Evp signature verification functions
Usage
Crypto Library (libcrypto, -lcrypto)
#include <openssl/evp.h>
int
EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *engine);
int
EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
int
EVP_VerifyFinal(EVP_MD_CTX *ctx, unsigned char *sigbuf, unsigned int siglen, EVP_PKEY *pkey);
int
EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
Overview
The EVP signature verification routines are a high-level interface to digital signatures.
EVP_VerifyInit_ex() sets up the verification context ctx to use the digest type. Before calling this function, obtain ctx from EVP_MD_CTX_new(3) or call EVP_MD_CTX_reset(3) on it. The engine argument is always ignored and passing NULL is recommended.
EVP_VerifyUpdate() hashes cnt bytes of data at d into the verification context ctx. This function can be called several times on the same ctx to include additional data.
EVP_VerifyFinal() verifies the data in ctx using the public key pkey and against the siglen bytes at sigbuf.
EVP_VerifyInit() initializes a verification context ctx to use the default implementation of digest type.
The EVP interface to digital signatures should almost always be used in preference to the low-level interfaces. This is because the code then becomes transparent to the algorithm used and much more flexible.
The call to EVP_VerifyFinal() internally finalizes a copy of the digest context. This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can be called later to digest and verify additional data.
Since only a copy of the digest context is ever finalized, the context must be cleaned up after use by calling EVP_MD_CTX_free(3), or a memory leak will occur.
EVP_VerifyInit_ex(), EVP_VerifyUpdate(), and EVP_VerifyInit() are implemented as macros.
Return values
EVP_VerifyInit_ex() and EVP_VerifyUpdate() return 1 for success and 0 for failure.
EVP_VerifyFinal() returns 1 for a correct signature, 0 for failure, and -1 if some other error occurred.
The error codes can be obtained by ERR_get_error(3).