PHP DES Encryption compatible with Delphi - encryption function - php

Question

I am trying to create the encrypt PHP algorithm from this thread:
how to sync encryption between delphi and php using dcpcrypt (see shunty's reply)
Here is what I have so far:
function encrypt($str, $key)
{
$keysize = mcrypt_get_key_size(MCRYPT_DES, MCRYPT_MODE_CBC);
$ivbytes = array(72, 163, 99, 62, 219, 111, 163, 114);
$iv = implode(array_map("chr", $ivbytes));
$pad = ord($str[strlen($str) - 1]);
$enc = substr($str, 0, strlen($str) - $pad);
$enc = base64_encode($str);
$k = mhash(MHASH_SHA1, $key);
//return substr($dec, 0, strlen($dec) - $pad);
$dec = mcrypt_encrypt(MCRYPT_DES, substr($k, 0, $keysize), $enc, MCRYPT_MODE_CBC, $iv);
return $dec;
}
I'm not sure what I'm doing wrong but testing it with this:
echo encrypt("this is a test", "test");
Gives the output: =ž«RCdrç­b˜hý’¯á·OÊ
when it should give: WRaG/8xlxqqcTAJ5UAk4DA==
Can anyone help me out in explaining where I am going wrong, would really appreciate the help I can get.
EDIT:
function encrypt_SO($str, $key)
{
$keysize = mcrypt_get_key_size(MCRYPT_DES, MCRYPT_MODE_CBC);
$ivbytes = array(72, 163, 99, 62, 219, 111, 163, 114);
$iv = implode(array_map("chr", $ivbytes));
$pad = ord($str[strlen($str) - 1]);
$enc = substr($str, 0, strlen($str) - $pad);
$k = mhash(MHASH_SHA1, $key);
//return substr($dec, 0, strlen($dec) - $pad);
$dec = mcrypt_encrypt(MCRYPT_DES, substr($k, 0, $keysize), $enc, MCRYPT_MODE_CBC, $iv);
return base64_encode($dec);
}
Moved the encoding to the end.
EDIT 2: Solution thanks to everyone's helpful posts:
function encrypt_SO($str, $key)
{
$keysize = mcrypt_get_key_size(MCRYPT_DES, MCRYPT_MODE_CBC);
$ivbytes = array(72, 163, 99, 62, 219, 111, 163, 114);
$iv = implode(array_map("chr", $ivbytes));
$k = mhash(MHASH_SHA1, $key);
$blocksize = mcrypt_get_block_size(MCRYPT_DES, MCRYPT_MODE_CBC);
$padsize = $blocksize - (strlen($str) % $blocksize);
$str .= str_repeat(chr($padsize), $padsize);
return base64_encode(mcrypt_encrypt(MCRYPT_DES, substr($k, 0, $keysize), $str, MCRYPT_MODE_CBC, $iv));
}

Answer 1

To answer your comment above:
Encrypt:
Get keysize and blocksize
Get IV - this should really be something random and properly generated but to work with DCPcrypt without specifying an IV manually you need to use the one provided.
Hash the key
Add the padding - you've got this bit wrong. For this example you need something like:
$blocksize = mcrypt_get_block_size(MCRYPT_DES, MCRYPT_MODE_CBC);
$padsize = $blocksize - (strlen($str) % $blocksize);
$str .= str_repeat(chr($padsize), $padsize);
Encrypt
Base64 encode
Decrypt:
Get keysize
Get IV - as above (must be the same as the one used to encrypt but, again, should really be properly cryptographically generated).
Hash the key
Base64 decode
Decrypt
Remove the padding