=pod =head1 NAME EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public key algorithm =head1 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); =head1 DESCRIPTION The EVP_PKEY_decrypt_init() function initializes a public key algorithm context using key B<pkey> for a decryption operation. The EVP_PKEY_decrypt() function performs a public key decryption operation using B<ctx>. The data to be decrypted is specified using the B<in> and B<inlen> parameters. If B<out> is B<NULL> then the maximum size of the output buffer is written to the B<outlen> parameter. If B<out> is not B<NULL> then before the call the B<outlen> parameter should contain the length of the B<out> buffer, if the call is successful the decrypted data is written to B<out> and the amount of data written to B<outlen>. =head1 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. =head1 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. =head1 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 */ =head1 SEE ALSO L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>, L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>, L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>, L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>, L<EVP_PKEY_verifyrecover(3)|EVP_PKEY_verifyrecover(3)>, L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> =head1 HISTORY These functions were first added to OpenSSL 1.0.0. =cut