how to sync encryption between delphi and php using dcpcrypt

Question

I\'m using Delphi 2009 and most of the answers I\'ve seen here are for 2010+ I am trying to sync encryption (delphi) to decryption (php) and failing.

generate the en

Answer 1

Several issues, I think :-)

• des.InitStr() internally creates an IV from 8 null bytes which it then encrypts. You need to use the same IV in your PHP.

• The sha1($key) produces a hex string rather than the actual bytes of the password. You need something like mhash instead.

• I couldn't manage to reproduce your $enc string with the given Delphi function.

• Unicode issues - the password and source text are going to be treated as unicode in Delphi.

• You seem to be base 64 encoding the source twice in the Delphi routines. des.EncryptString and des.DecryptString produce and consume base 64 encoded strings so no need to do it again.

• Padding

Based on my previous answer here - this is my suggestion:

function EncryptStringDES: string;
var
  des: TDCP_des;
  src, enc, b64: TBytes;
  index, slen, bsize, padsize: integer;
begin
  des:=tdcp_des.Create(nil);
  try
    des.InitStr(AnsiString('test'), tdcp_sha1);

    src := TEncoding.UTF8.GetBytes('this is a test');
    slen := Length(src);
    // Add padding
    bsize := des.BlockSize div 8;
    padsize := bsize - (slen mod bsize);
    Inc(slen, padsize);
    SetLength(src, slen);
    for index := padsize downto 1 do
    begin
      src[slen - index] := padsize;
    end;

    SetLength(enc, slen);
    des.EncryptCBC(src[0], enc[0], slen);
    result := EncdDecd.EncodeBase64(@enc[0], Length(enc));
  finally
    des.Free;
  end;
end;

function DecryptStringDES(ASource: string): string;
var
  des: TDCP_des;
  key, src, dec, b64: TBytes;
  pad, slen: integer;
begin
  des := TDCP_des.Create(nil);
  try
    des.InitStr(AnsiString('test'), tdcp_sha1);

    src := EncdDecd.DecodeBase64(AnsiString(ASource));
    slen := Length(src);
    SetLength(dec, slen);
    des.DecryptCBC(src[0], dec[0], slen);

    // Remove padding
    pad := dec[slen - 1];
    SetLength(dec, slen - pad);

    result := TEncoding.UTF8.GetString(dec);
  finally
    des.Free;
  end;
end;

and the PHP: