Hi Lars, please reply to all recipients.
On Tue, 02 Jun 2015 12:54:54 +0300 Lars Noodén <lars.noo...@gmail.com> wrote: > I have a calculated variable $otp which is decrypted using AES key $key. > If the variable was properly decrypted, the first six bytes of the > decrypted data should match what is in $userid, I think. > > How do I extract the first six bytes of $plaintext and compare it to > what's in $userid ? > To extract the first six bytes, use the substr function: http://perldoc.perl.org/functions/substr.html The command «my $first_6_bytes = substr($plaintext, 0, 6);» ought to do the tricks (but there may be some complications due to Unicode and charsets/encoding). To compare it to $userid, you can use "eq", "cmp", etc. See: http://perldoc.perl.org/perlop.html It seems that $userid is encoded in hex so you'll need to convert it to a plain binary string first. Regards, Shlomi Fish > Regards, > Lars > > > #!/usr/bin/perl > > use strict; > use warnings; > use Convert::ModHex qw(modhex2hex); > use Crypt::Rijndael; > > my $input = qq(ujvrgjnigiibvrjctcflercebvcvhicbnhhheliclnfh); > my $key = qq(83b396b8f996fa1be3dafdc3f0eefc21); > my $userid = qq(aa6d0a6e8a65); > > my ( $publicid, $otp ) = ( $input =~ /^(.*)(.{32})$/ ); # OTP 32B > > my $hex = modhex2hex($otp); > print qq(publicid=$publicid\n$otp\n$hex\n\n); > > my $cipher = Crypt::Rijndael->new( $key, Crypt::Rijndael::MODE_CBC() ); > > my $plaintext = $cipher->decrypt($hex); > > print qq(\np=$plaintext\n); > > exit( 0 ); > -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ List of Portability Libraries - http://shlom.in/port-libs Daniel: Yeah, those guys [= NSA] don’t publish… Andrew: They perish, man. — http://www.shlomifish.org/humour/Summerschool-at-the-NSA/ Please reply to list if it's a mailing list post - http://shlom.in/reply . -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
