help tranlating perl expressions

[David Bear]

I am trying to translate some perl code to python and I need some advice on
making fixed sized strings. The perl code creates a sha1 signatured using a
key and a 'pad'. It creates fixed sized strings as follows:

 my $klen = length($key);
 my $blen = 64;
 my $ipad = chr(0x36)x$blen;
 my $opad = chr(0x5c)x$blen;

I don't know if I ever seen any way in python of created a fixed size
string. Can anyone show me how to implement the same statements in python?

Next, it zero-fills a string to a certain size.

 if($klen <= $blen) {
  $key .= "\0"x($blen-length($key)); #zero-fill to blocksize
 } else {
  $key = sha1($key);                 #if longer, pre-hash key
 }

Finally it concatenates and xors these strings together like this:

 return sha1($key^$opad . sha1($key^$ipad . $data));

I when python XOR's strings, is it the same as when perl xor's them?

-- 
David Bear
-- let me buy your intellectual property, I want to own your thoughts --