EVP_PKEY_decrypt_init, EVP_PKEY_decrypt -- decrypt using a public key algorithm
Synopsis
#include <openssl/evp.h>
int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx,
unsigned char *out, size_t *outlen,
const unsigned char *in, size_t inlen);
DESCRIPTION
The EVP_PKEY_decrypt_init() function initializes a public key
algorithm context using key pkey for
a decryption operation.
The EVP_PKEY_decrypt() function performs a public key decryption
operation using ctx. The data to be
decrypted is specified using the in
and inlen parameters. If out is NULL
then the maximum size of the output buffer is written to the
outlen parameter. If out is not NULL then before the call the outlen parameter should contain the length of
the out buffer, if the call is
successful the decrypted data is written to out and the amount of data written to
outlen.
NOTES
After the call to EVP_PKEY_decrypt_init() algorithm specific control
operations can be performed to set any appropriate parameters for the
operation.
The function EVP_PKEY_decrypt() can be called more than once on the
same context if several operations are performed using the same
parameters.
RETURN VALUES
EVP_PKEY_decrypt_init() and EVP_PKEY_decrypt() return 1 for success
and 0 or a negative value for failure. In particular a return value
of -2 indicates the operation is not supported by the public key
algorithm.
EXAMPLE
Decrypt data using OAEP (for RSA keys):
#include <openssl/evp.h>
#include <openssl/rsa.h>
EVP_PKEY_CTX *ctx;
unsigned char *out, *in;
size_t outlen, inlen;
EVP_PKEY *key;
/* NB: assumes key in, inlen are already set up
* and that key is an RSA private key
*/
ctx = EVP_PKEY_CTX_new(key);
if (!ctx)
/* Error occurred */
if (EVP_PKEY_decrypt_init(ctx) <= 0)
/* Error */
if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0)
/* Error */
/* Determine buffer length */
if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0)
/* Error */
out = OPENSSL_malloc(outlen);
if (!out)
/* malloc failure */
if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0)
/* Error */
/* Decrypted data is outlen bytes written to buffer out */
