{$MINENUMSIZE 1}
  TOpenPGPPKAlgorithm = (
    pkRSA                    = 1,
    pkRSAEncryptOnly         = 2,
    pkRSASignOnly            = 3,
    pkElgamalEncryptOnly     = 16,
    pkDSA                    = 17,
    pkReservedEC             = 18,
    pkReservedECDSA          = 19,
    pkReserved20             = 20,
    pkReservedDH             = 21,
    pkPrivate100             = 100,
    pkPrivate101             = 101,
    pkPrivate102             = 102,
    pkPrivate103             = 103,
    pkPrivate104             = 104,
    pkPrivate105             = 105,
    pkPrivate106             = 106,
    pkPrivate107             = 107,
    pkPrivate108             = 108,
    pkPrivate109             = 109,
    pkPrivate110             = 110
  );

function TPGPTag_Signature.ReadBody(PartOf: ITagStreamReader; Source: IIOReadable): OpenPGPResult; stdcall;
var
  reader: IIOTypedReader;
  subpack: IIOReadable;
  wb: Byte;
  ww: Word;
begin
  // some init

  reader:= TIOTypedReader.Create(Source);
  if not OpenPGPSuccess(reader.ReadByte(fVersion), Result) then
    Exit;
  case fVersion of
    2, 3: {...};
    4: begin
      if not OpenPGPSuccess(reader.ReadByte(wb), Result) then
        Exit;
      fSignatureType:= TOpenPGPSignatureType(wb);
      TraceDebug('V4 Signature: %s', [SignatureTypeToStr(fSignatureType)]);
      if not OpenPGPSuccess(reader.ReadByte(wb), Result) then
        Exit;
      fPKAlgo:= TOpenPGPPKAlgorithm(wb);
      {...}
    end;
  else
    TraceError('Unsupported Signature version: %d', [fVersion]);
    Exit(OPENPGP_ERROR_PACKET_INVALID_DATA);
  end;
  case fPKAlgo of
    pkRSA, pkRSASignOnly: begin
      fRSA_mdn:= TMPInteger.Create;
      if not OpenPGPSuccess(fRSA_mdn.Read(Source), Result) then
        Exit;
    end;
    pkDSA: begin
      fDSA_r:= TMPInteger.Create;
      fDSA_s:= TMPInteger.Create;
      if not OpenPGPSuccess(fDSA_r.Read(Source), Result) then
        Exit;
      if not OpenPGPSuccess(fDSA_s.Read(Source), Result) then
        Exit;
    end;
  else
    TraceWarn('Signature.ReadBody: Unknown Signature Algorithm: %s', [PKAlgorithmToStr(fPKAlgo)]);
    Exit(OPENPGP_ERROR_PACKET_INVALID_DATA);
  end;
  Result:= OPENPGP_ERROR_NOERROR;
end;

function SignatureTypeToStr(const X: TOpenPGPSignatureType): String;
begin
  case X of
    stBinaryDocument              : Result:= 'BinaryDocument';
    stCanonicalDocument           : Result:= 'CanonicalDocument';
    stStandalone                  : Result:= 'Standalone';

    stUserIDCertificationGeneric  : Result:= 'UserIDCertificationGeneric';
    stUserIDCertificationPersona  : Result:= 'UserIDCertificationPersona';
    stUserIDCertificationCasual   : Result:= 'UserIDCertificationCasual';
    stUserIDCertificationPositive : Result:= 'UserIDCertificationPositive';

    stSubkeyBinding               : Result:= 'SubkeyBinding';
    stPrimaryKeyBinding           : Result:= 'PrimaryKeyBinding';

    stDirectKey                   : Result:= 'DirectKey';

    stKeyRevocation               : Result:= 'KeyRevocation';
    stSubKeyRevocation            : Result:= 'SubKeyRevocation';

    stCertificationRevocation     : Result:= 'CertificationRevocation';

    stTimestamp                   : Result:= 'Timestamp';

    stThirdPartyConfirmation      : Result:= 'ThirdPartyConfirmation';
  else
    Str(Ord(X), Result);
  end;
end;