Hello Monks,

I have been reading the guide to MIX files at https://moddingwiki.shikadi.net/wiki/MIX_Format_(Westwood) and have been having a go at decoding some. My problem is dealing with the RSA encrypted header using Crypt:Openssl::RSA, specifically loading the key.

The aforementioned site lists the modulus as AihRvNoIbTn85FZRYNZRcT+i6KpU+maCsEqr3Q5q+LDB5tH7Tz2qQ38V and the private exponent as AigKVje8mROcR8QixnxUEF5b29Curkq01DNDWCdOG99XBqH79OaCiTCB (both as BASE64 / DER encoded integers) and the public exponent as 0x10001. This not being the most helpful format, I figured that the best way to get it into Crypt::Openssl::RSA was via the new_key_from_parameters() method.

I converted both the modulus and private exponent to hex via an online decoder for use with Crypt::OpenSSL::Bignum->new_from_hex.

The issue appears to be that after loading the key material, check_key returns false, triggering the die with "invalid key"

#!/usr/bin/perl

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

my $pub = '51BCDA086D39FCE4565160D651713FA2E8AA54FA6682B04AABDD0E6AF8B
+0C1E6D1FB4F3DAA437F15';
my $priv = '0A5637BC99139C47C422C67C54105E5BDBD0AEAE4AB4D4334358274E1B
+DF5706A1FBF4E682893081';
my $expo = '10001';

my $n = Crypt::OpenSSL::Bignum->new_from_hex($pub);
my $e = Crypt::OpenSSL::Bignum->new_from_hex($expo);
my $d = Crypt::OpenSSL::Bignum->new_from_hex($priv);

my $rsa = Crypt::OpenSSL::RSA->new_key_from_parameters($n, $e, $d);

die "invalid key" unless $rsa->check_key;

[download]

There doesn't appear to be a lot to screw up, so I can't see where I've got it wrong, unless I've done something stupid decoding the BASE64/DER data. I've been over it several times. If anyone can offer any words of wisdom, I would be extremely grateful.

Thanks,
BOfH

In reply to Importing keys into Crypt::Openssl::RSA by BOfH

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