The code below is a Perl version of an encryption/hashing algorithm used by OpenOffice to generate pseudo passwords for Excel worksheets. The input is a single 16 bit integer.

Does anyone recognise the algorithm or methodology used.

Apologies for being off-topic.

sub Decode {

    my $nPasswd  = shift || 0;
    my $sPasswd  = '';
    my $sDummy   = '';
    my $nLen     = 9;
    my $nDummy   = 0;
    my $nNewChar = 0;

    $nPasswd ^= 0xCE4B;
    $nDummy = $nPasswd;

    while ( !($nDummy & 0x8000) && $nLen ) {
        $nLen--;
        $nDummy <<= 1;
    }

    if ( !$nLen ) {
        $nLen = 2;
    }

    if ( ($nLen ^ $nPasswd) & 0x0001 ) {
        $nLen++;
    }

    if ( $nLen == 9 ) {
        $nLen = 10;
        $nPasswd ^= 0x8001;
    }

    $nPasswd ^= $nLen;

    if ( $nLen < 9 ) {
        $nPasswd <<= (8 - $nLen);
    }

    for ( my $iChar = $nLen; $iChar > 0; $iChar-- ) {
        if ($iChar == 10) {
            $nNewChar = ($nPasswd & 0xC000) | 0x0400;
            $nPasswd ^= $nNewChar;
            $nNewChar >>= 2;
        } elsif ($iChar == 9) {
            $nNewChar = 0x4200;
            $nPasswd ^= $nNewChar;
            $nNewChar >>= 1;

        } elsif ($iChar == 1) {
            $nNewChar = $nPasswd & 0xFF00;
        } else {
            $nNewChar = ($nPasswd & 0xE000) ^ 0x2000;
            if ( !$nNewChar ) {
                $nNewChar = ($nPasswd & 0xF000) ^ 0x1800;
            }
            if ( $nNewChar == 0x6000 ) {
                $nNewChar = 0x6100;
            }
            $nPasswd ^= $nNewChar;
            $nPasswd <<= 1;
        }

        $nNewChar >>= 8;
        $nNewChar &=  0x00FF;
        $sPasswd  .=  chr $nNewChar;
    }
    print "<$sPasswd>\n\n";
}
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John.
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