flutter / third_party / openssl / 4b1b629725970384d6cf4dafe9e83e54859574cd / . / doc / man3 / RSA_public_encrypt.pod

=pod | |

=head1 NAME | |

RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography | |

=head1 SYNOPSIS | |

#include <openssl/rsa.h> | |

The following functions have been deprecated since OpenSSL 3.0, and can be | |

hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value, | |

see L<openssl_user_macros(7)>: | |

int RSA_public_encrypt(int flen, const unsigned char *from, | |

unsigned char *to, RSA *rsa, int padding); | |

int RSA_private_decrypt(int flen, const unsigned char *from, | |

unsigned char *to, RSA *rsa, int padding); | |

=head1 DESCRIPTION | |

Both of the functions described on this page are deprecated. | |

Applications should instead use L<EVP_PKEY_encrypt_init_ex(3)>, | |

L<EVP_PKEY_encrypt(3)>, L<EVP_PKEY_decrypt_init_ex(3)> and | |

L<EVP_PKEY_decrypt(3)>. | |

RSA_public_encrypt() encrypts the B<flen> bytes at B<from> (usually a | |

session key) using the public key B<rsa> and stores the ciphertext in | |

B<to>. B<to> must point to RSA_size(B<rsa>) bytes of memory. | |

B<padding> denotes one of the following modes: | |

=over 4 | |

=item RSA_PKCS1_PADDING | |

PKCS #1 v1.5 padding. This currently is the most widely used mode. | |

However, it is highly recommended to use RSA_PKCS1_OAEP_PADDING in | |

new applications. SEE WARNING BELOW. | |

=item RSA_PKCS1_OAEP_PADDING | |

EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty | |

encoding parameter. This mode is recommended for all new applications. | |

=item RSA_NO_PADDING | |

Raw RSA encryption. This mode should I<only> be used to implement | |

cryptographically sound padding modes in the application code. | |

Encrypting user data directly with RSA is insecure. | |

=back | |

B<flen> must not be more than RSA_size(B<rsa>) - 11 for the PKCS #1 v1.5 | |

based padding modes, not more than RSA_size(B<rsa>) - 42 for | |

RSA_PKCS1_OAEP_PADDING and exactly RSA_size(B<rsa>) for RSA_NO_PADDING. | |

When a padding mode other than RSA_NO_PADDING is in use, then | |

RSA_public_encrypt() will include some random bytes into the ciphertext | |

and therefore the ciphertext will be different each time, even if the | |

plaintext and the public key are exactly identical. | |

The returned ciphertext in B<to> will always be zero padded to exactly | |

RSA_size(B<rsa>) bytes. | |

B<to> and B<from> may overlap. | |

RSA_private_decrypt() decrypts the B<flen> bytes at B<from> using the | |

private key B<rsa> and stores the plaintext in B<to>. B<flen> should | |

be equal to RSA_size(B<rsa>) but may be smaller, when leading zero | |

bytes are in the ciphertext. Those are not important and may be removed, | |

but RSA_public_encrypt() does not do that. B<to> must point | |

to a memory section large enough to hold the maximal possible decrypted | |

data (which is equal to RSA_size(B<rsa>) for RSA_NO_PADDING, | |

RSA_size(B<rsa>) - 11 for the PKCS #1 v1.5 based padding modes and | |

RSA_size(B<rsa>) - 42 for RSA_PKCS1_OAEP_PADDING). | |

B<padding> is the padding mode that was used to encrypt the data. | |

B<to> and B<from> may overlap. | |

=head1 RETURN VALUES | |

RSA_public_encrypt() returns the size of the encrypted data (i.e., | |

RSA_size(B<rsa>)). RSA_private_decrypt() returns the size of the | |

recovered plaintext. A return value of 0 is not an error and | |

means only that the plaintext was empty. | |

On error, -1 is returned; the error codes can be | |

obtained by L<ERR_get_error(3)>. | |

=head1 WARNINGS | |

Decryption failures in the RSA_PKCS1_PADDING mode leak information | |

which can potentially be used to mount a Bleichenbacher padding oracle | |

attack. This is an inherent weakness in the PKCS #1 v1.5 padding | |

design. Prefer RSA_PKCS1_OAEP_PADDING. | |

=head1 CONFORMING TO | |

SSL, PKCS #1 v2.0 | |

=head1 SEE ALSO | |

L<ERR_get_error(3)>, L<RAND_bytes(3)>, | |

L<RSA_size(3)> | |

=head1 HISTORY | |

Both of these functions were deprecated in OpenSSL 3.0. | |

=head1 COPYRIGHT | |

Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. | |

Licensed under the Apache License 2.0 (the "License"). You may not use | |

this file except in compliance with the License. You can obtain a copy | |

in the file LICENSE in the source distribution or at | |

L<https://www.openssl.org/source/license.html>. | |

=cut |