function String2Hex(const Buffer: AnsiString): string;

begin

  SetLength(Result, Length(Buffer) * 2);

  BinToHex(PAnsiChar(Buffer), PChar(Result), Length(Buffer));

end;

​

function Hex2String(const Buffer: string): AnsiString;

begin

  SetLength(Result, Length(Buffer) div 2);

  HexToBin(PChar(Buffer), PAnsiChar(Result), Length(Result));

end;

​

...//caller function

var

  hex: string;

  str: AnsiString;

begin

  hex := String2Hex('stackoverflow');

  ShowMessage(hex); // shows '737461636B6F766572666C6F77'

  str := Hex2String(hex);

  ShowMessage(str); // shows 'stackoverflow'

end;