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 B<pkey> for a decryption operation. 22 23The EVP_PKEY_decrypt_init_ex() function initializes a public key algorithm 24context using key B<pkey> for a decryption operation and sets the 25algorithm specific B<params>. 26 27The EVP_PKEY_decrypt() function performs a public key decryption operation 28using B<ctx>. The data to be decrypted is specified using the B<in> and 29B<inlen> parameters. If B<out> is B<NULL> then the maximum size of the output 30buffer is written to the B<outlen> parameter. If B<out> is not B<NULL> then 31before the call the B<outlen> parameter should contain the length of the 32B<out> buffer, if the call is successful the decrypted data is written to 33B<out> and the amount of data written to B<outlen>. 34 35=head1 NOTES 36 37After the call to EVP_PKEY_decrypt_init() algorithm specific control 38operations can be performed to set any appropriate parameters for the 39operation. These operations can be included in the EVP_PKEY_decrypt_init_ex() 40call. 41 42The function EVP_PKEY_decrypt() can be called more than once on the same 43context if several operations are performed using the same parameters. 44 45=head1 RETURN VALUES 46 47EVP_PKEY_decrypt_init(), EVP_PKEY_decrypt_init_ex() and EVP_PKEY_decrypt() 48return 1 for success and 0 or a negative value for failure. In particular a 49return value of -2 indicates the operation is not supported by the public key 50algorithm. 51 52=head1 EXAMPLES 53 54Decrypt data using OAEP (for RSA keys): 55 56 #include <openssl/evp.h> 57 #include <openssl/rsa.h> 58 59 EVP_PKEY_CTX *ctx; 60 ENGINE *eng; 61 unsigned char *out, *in; 62 size_t outlen, inlen; 63 EVP_PKEY *key; 64 65 /* 66 * NB: assumes key, eng, in, inlen are already set up 67 * and that key is an RSA private key 68 */ 69 ctx = EVP_PKEY_CTX_new(key, eng); 70 if (!ctx) 71 /* Error occurred */ 72 if (EVP_PKEY_decrypt_init(ctx) <= 0) 73 /* Error */ 74 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0) 75 /* Error */ 76 77 /* Determine buffer length */ 78 if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0) 79 /* Error */ 80 81 out = OPENSSL_malloc(outlen); 82 83 if (!out) 84 /* malloc failure */ 85 86 if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0) 87 /* Error */ 88 89 /* Decrypted data is outlen bytes written to buffer out */ 90 91=head1 SEE ALSO 92 93L<EVP_PKEY_CTX_new(3)>, 94L<EVP_PKEY_encrypt(3)>, 95L<EVP_PKEY_sign(3)>, 96L<EVP_PKEY_verify(3)>, 97L<EVP_PKEY_verify_recover(3)>, 98L<EVP_PKEY_derive(3)> 99 100=head1 HISTORY 101 102These functions were added in OpenSSL 1.0.0. 103 104=head1 COPYRIGHT 105 106Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved. 107 108Licensed under the Apache License 2.0 (the "License"). You may not use 109this file except in compliance with the License. You can obtain a copy 110in the file LICENSE in the source distribution or at 111L<https://www.openssl.org/source/license.html>. 112 113=cut 114