MD5 Hashing in Delphi

Calculate MD5 Checksum for a File or String using Delphi

The MD5 Message-Digest algorithm is a cryptographic hash function. MD5 is commonly used to check the integrity of files. An MD5 hash value is a 32 digit hexadecimal number.

MD5 for files

Using Delphi, you can easily create a function to calculate the MD5 hash for a given file. All you need is included in two units (part of Indy): IdHashMessageDigest and idHash.

uses IdHashMessageDigest, idHash;

//returns MD5 has for a file
function MD5(const fileName : string) : string;
var
  idmd5 : TIdHashMessageDigest5;
  fs : TFileStream;
  hash : T4x4LongWordRecord;
begin
  idmd5 := TIdHashMessageDigest5.Create;
  fs := TFileStream.Create(fileName, fmOpenRead OR fmShareDenyWrite) ;
  try
    result := idmd5.AsHex(idmd5.HashValue(fs)) ;
  finally
    fs.Free;
    idmd5.Free;
  end;
end;

You can use MD5 file hashing to enusure that after a (some kind of file) transfer the file has arrived intact.