>perl -wMstrict -le
"my $binary = pack 'H*', '03762cefa7ffe5';
 printf '%02x ', $_ for unpack 'C*', $binary;  print '';
 ;;
 my ($p, $q) = unpack 'xCC', $binary;
 my $pairs   = (length($binary) - 3) / 2;
 my $k       = pack 'C*', 0, 0, 0, ($p, $q) x $pairs;
 printf '%02x ', $_ for unpack 'C*', $k;  print '';
 ;;
 my $decode = $binary ^ $k;
 printf '%02x ', $_ for unpack 'C*', $decode;
"
03 76 2c ef a7 ff e5
00 00 00 76 2c 76 2c
03 76 2c 99 8b 89 c9