1=pod 2 3=head1 NAME 4 5EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public key algorithm 6 7=head1 SYNOPSIS 8 9 #include <openssl/evp.h> 10 11 int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx); 12 int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx, 13 unsigned char *out, size_t *outlen, 14 const unsigned char *in, size_t inlen); 15 16=head1 DESCRIPTION 17 18The EVP_PKEY_decrypt_init() function initializes a public key algorithm 19context using key B<pkey> for a decryption operation. 20 21The EVP_PKEY_decrypt() function performs a public key decryption operation 22using B<ctx>. The data to be decrypted is specified using the B<in> and 23B<inlen> parameters. If B<out> is B<NULL> then the maximum size of the output 24buffer is written to the B<outlen> parameter. If B<out> is not B<NULL> then 25before the call the B<outlen> parameter should contain the length of the 26B<out> buffer, if the call is successful the decrypted data is written to 27B<out> and the amount of data written to B<outlen>. 28 29=head1 NOTES 30 31After the call to EVP_PKEY_decrypt_init() algorithm specific control 32operations can be performed to set any appropriate parameters for the 33operation. 34 35The function EVP_PKEY_decrypt() can be called more than once on the same 36context if several operations are performed using the same parameters. 37 38=head1 RETURN VALUES 39 40EVP_PKEY_decrypt_init() and EVP_PKEY_decrypt() return 1 for success and 0 41or a negative value for failure. In particular a return value of -2 42indicates the operation is not supported by the public key algorithm. 43 44=head1 EXAMPLE 45 46Decrypt data using OAEP (for RSA keys): 47 48 #include <openssl/evp.h> 49 #include <openssl/rsa.h> 50 51 EVP_PKEY_CTX *ctx; 52 unsigned char *out, *in; 53 size_t outlen, inlen; 54 EVP_PKEY *key; 55 /* NB: assumes key in, inlen are already set up 56 * and that key is an RSA private key 57 */ 58 ctx = EVP_PKEY_CTX_new(key); 59 if (!ctx) 60 /* Error occurred */ 61 if (EVP_PKEY_decrypt_init(ctx) <= 0) 62 /* Error */ 63 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0) 64 /* Error */ 65 66 /* Determine buffer length */ 67 if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0) 68 /* Error */ 69 70 out = OPENSSL_malloc(outlen); 71 72 if (!out) 73 /* malloc failure */ 74 75 if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0) 76 /* Error */ 77 78 /* Decrypted data is outlen bytes written to buffer out */ 79 80=head1 SEE ALSO 81 82L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>, 83L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>, 84L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>, 85L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>, 86L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>, 87L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> 88 89=head1 HISTORY 90 91These functions were first added to OpenSSL 1.0.0. 92 93=cut 94