/usr/man2/cat.3/EVP_PKEY_decrypt_init.3.Z(/usr/man2/cat.3/EVP_PKEY_decrypt_init.3.Z)

NAME

       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 opera-
       tion 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 parame-
       ters.

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 */

SEE ALSO

       EVP_PKEY_CTX_new(3), EVP_PKEY_encrypt(3), EVP_PKEY_sign(3),
       EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3), EVP_PKEY_derive(3)

HISTORY

       These functions were first added to OpenSSL 1.0.0.

1.0.2t                            2019-09-10               EVP_PKEY_decrypt(3)
See also EVP_PKEY_decrypt(3)