I would appreciate any donations. Wishlist or send e-mail type donations to maekawa AT daemon-systems.org.

Thank you.

EVP_PKEY_decrypt(3)                 OpenSSL                EVP_PKEY_decrypt(3)

       EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public key

       libcrypto, -lcrypto

        #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);

       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.

       After the call to EVP_PKEY_decrypt_init() algorithm specific control
       operations can be performed to set any appropriate parameters for the

       The function EVP_PKEY_decrypt() can be called more than once on the
       same context if several operations are performed using the same

       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.

       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 */

       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)

       These functions were first added to OpenSSL 1.0.0.

1.0.2k                            2013-02-05               EVP_PKEY_decrypt(3)