/usr/man/cat.3/EVP_PKEY_decrypt_init.3

EVP_PKEY_decrypt(3)          OpenSSL          EVP_PKEY_decrypt(3)

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 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>

1.0.2t               Last change: 2019-09-10                    1

EVP_PKEY_decrypt(3)          OpenSSL          EVP_PKEY_decrypt(3)

      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               Last change: 2019-09-10                    2

See also EVP_PKEY_decrypt(3)