in reply to RSA encrypt but no decrypt. What is the problem?

It appears to be a problem* with the key you've provided. Adding die "invalid key" unless $rsa->check_key; causes the script to die. The following works for me:

use warnings;
use strict;
use Crypt::OpenSSL::RSA;
use Crypt::OpenSSL::Bignum;
use Data::Dump;

my $rsa = Crypt::OpenSSL::RSA->generate_key(1024);
my $priv = $rsa->get_private_key_string;
my $ciphertext = $rsa->encrypt("Hello");

my $rsa2 = Crypt::OpenSSL::RSA->new_private_key($priv);
my $plaintext = $rsa2->decrypt($ciphertext);
dd $plaintext;

my %params;
@params{qw/n e d p q/, 'd mod (p-1)', 'd mod (q-1)', '1/q mod p'}
    = map { $_->to_hex } $rsa->get_key_parameters;
dd \%params;

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* Update: Specifically, when I replace your d and n parameters with newly generated ones, your code works for me (as long as both sides use pkcs1_padding or pkcs1_oaep_padding, the latter being the default). Note that $rsa->check_key checks for the presence of the parameters n, e, d, p, and q, you're not giving it p and q (though the decryption still works). If you were to provide Crypt::OpenSSL::RSA with only n and e, that would tell the module it's a public key only. I'm not sure why you're working with keys the way you've shown in your post?

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Re^2: RSA encrypt but no decrypt. What is the problem? (updated)
by Forb (Novice) on May 08, 2021 at 11:14 UTC

    Yes, thanks, I have checked, your code works for me, but it is not convenient for me. In your code, encryption and decryption is done within a single script. In practice, this is not convenient. I would like one script to encrypt the message and another script to decrypt the message. In this case, it is not possible to use Crypt :: OpenSSL :: RSA-> generate_key (1024); in both scripts. The best option is to use the parameters n, e, and d.

[reply]
      The best option is to use the parameters n, e, and d.

      Personally, I'd use the string representation of the keys, since that's also a standard way of sharing them, but you're free to use the parameters if you wish. My code shows examples of both.

[reply]

        Two questions:

        1. Does your method mean that in Perl for RSA I must use the generate_key() function to generate keys? Can I do without this function in Perl and set the parameters n, e, d myself? For example, in the C-language, this is possible.

        2. I tried adding one line to your code:

        my $plaintext = $rsa2->public_decrypt($ciphertext);

        but unfortunately this script gives an error: "unknown padding type". Of course, the error can be avoided by adding one more line:

        $rsa2->use_no_padding();

        But as a result, the decryption of the text will not be correct. Do you think why?

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