1=pod 2 3=head1 NAME 4 5EVP_PKEY_decrypt_init, EVP_PKEY_decrypt_init_ex, 6EVP_PKEY_decrypt - decrypt using a public key algorithm 7 8=head1 SYNOPSIS 9 10 #include <openssl/evp.h> 11 12 int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx); 13 int EVP_PKEY_decrypt_init_ex(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]); 14 int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx, 15 unsigned char *out, size_t *outlen, 16 const unsigned char *in, size_t inlen); 17 18=head1 DESCRIPTION 19 20The EVP_PKEY_decrypt_init() function initializes a public key algorithm 21context using key I<pkey> for a decryption operation. 22 23The EVP_PKEY_decrypt_init_ex() function initializes a public key algorithm 24context using key I<pkey> for a decryption operation and sets the 25algorithm specific I<params>. 26 27The EVP_PKEY_decrypt() function performs a public key decryption operation 28using I<ctx>. The data to be decrypted is specified using the I<in> and 29I<inlen> parameters. If I<out> is NULL then the minimum required size of 30the output buffer is written to the I<*outlen> parameter. 31 32If I<out> is not NULL then before the call the I<*outlen> parameter must 33contain the length of the I<out> buffer. If the call is successful the 34decrypted data is written to I<out> and the amount of the decrypted data 35written to I<*outlen>, otherwise an error is returned. 36 37=head1 NOTES 38 39After the call to EVP_PKEY_decrypt_init() algorithm specific control 40operations can be performed to set any appropriate parameters for the 41operation. These operations can be included in the EVP_PKEY_decrypt_init_ex() 42call. 43 44The function EVP_PKEY_decrypt() can be called more than once on the same 45context if several operations are performed using the same parameters. 46 47=head1 RETURN VALUES 48 49EVP_PKEY_decrypt_init(), EVP_PKEY_decrypt_init_ex() and EVP_PKEY_decrypt() 50return 1 for success and 0 or a negative value for failure. In particular a 51return value of -2 indicates the operation is not supported by the public key 52algorithm. 53 54=head1 EXAMPLES 55 56Decrypt data using OAEP (for RSA keys): 57 58 #include <openssl/evp.h> 59 #include <openssl/rsa.h> 60 61 EVP_PKEY_CTX *ctx; 62 ENGINE *eng; 63 unsigned char *out, *in; 64 size_t outlen, inlen; 65 EVP_PKEY *key; 66 67 /* 68 * NB: assumes key, eng, in, inlen are already set up 69 * and that key is an RSA private key 70 */ 71 ctx = EVP_PKEY_CTX_new(key, eng); 72 if (!ctx) 73 /* Error occurred */ 74 if (EVP_PKEY_decrypt_init(ctx) <= 0) 75 /* Error */ 76 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_OAEP_PADDING) <= 0) 77 /* Error */ 78 79 /* Determine buffer length */ 80 if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0) 81 /* Error */ 82 83 out = OPENSSL_malloc(outlen); 84 85 if (!out) 86 /* malloc failure */ 87 88 if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0) 89 /* Error */ 90 91 /* Decrypted data is outlen bytes written to buffer out */ 92 93=head1 SEE ALSO 94 95L<EVP_PKEY_CTX_new(3)>, 96L<EVP_PKEY_encrypt(3)>, 97L<EVP_PKEY_sign(3)>, 98L<EVP_PKEY_verify(3)>, 99L<EVP_PKEY_verify_recover(3)>, 100L<EVP_PKEY_derive(3)> 101 102=head1 HISTORY 103 104These functions were added in OpenSSL 1.0.0. 105 106=head1 COPYRIGHT 107 108Copyright 2006-2022 The OpenSSL Project Authors. All Rights Reserved. 109 110Licensed under the Apache License 2.0 (the "License"). You may not use 111this file except in compliance with the License. You can obtain a copy 112in the file LICENSE in the source distribution or at 113L<https://www.openssl.org/source/license.html>. 114 115=cut 116