Delphi 11.1与XE5数据类型差异致Lockbox加密结果不一致问题

我正在将Delphi XE5应用迁移至Delphi 11.1，使用相同版本的Lockbox组件时，得到的加密字符串却不一致。

调试发现调用链为：EncryptSymStr() → TCodec.EncryptString() → TSimpleCodec.EncryptString() → Stream_to_Base64()，在调用Stream_to_Base64()之前，所有中间内容均完全一致。

首次差异出现在Stream_to_Base64()函数内的ThreeBytes变量：

• 在XE5中，ThreeBytes的值为：

  ThreeBytes [0] = 253
             [1] = 206
             [2] = 0
  

• 在Delphi 11中，ThreeBytes的值为：

  ThreeBytes [0] = 105
             [1] = 155
             [2] = 1
  

由于两个环境使用的Lockbox版本相同，推测问题源于XE5到11.1之间的数据类型差异。相关代码如下：

var
oCodeRDL:   TCodec;

cmdstr := '...---... ETS4162735 BUBBA '; 
cmdStr := EncryptSymStr(cmdStr);

function EncryptSymStr(Value: string): string;
var
   CipherText: ansistring;
begin
   if AllowEncryption then
   begin
      oCodeRDL.EncryptString(Value, CipherText);
      Result := CipherText;
   end
   else
      Result := Value;      
end;

procedure TCodec.EncryptString(
  const Plaintext: string; var CipherText_Base64: ansistring);
begin
InterfacesAreCached := True;
BeginEncDec;
FCodec.EncryptString( Plaintext, CipherText_Base64);
EndEncDec
end;

procedure TSimpleCodec.EncryptString(
  const Plaintext: string;
  var CipherText_Base64: ansistring);
var
  Temp: TMemoryStream;
  L: integer;
begin
Temp := TMemoryStream.Create;
try
  Begin_EncryptMemory( Temp);
  L := Length( Plaintext) * SizeOf( Char);
  if L > 0 then
    EncryptMemory( Plaintext[1], L);
  End_EncryptMemory;
  if FisUserAborted then
      CipherText_Base64 := ''
    else
      begin
      Temp.Position := 0;
      if isNotBase64Converter then
          CipherText_Base64 := Stream_to_Base64( Temp)
        else
          // If its already a Base64 encoder, no point in double-encoding it as base64.
          CipherText_Base64 := Stream_to_AnsiString( Temp)
      end
finally
  Temp.Free
end;

function  Stream_to_Base64( Source: TStream): ansistring;
var
  ThreeBytes: packed array[ 0..2 ] of byte;
  BytesRead: integer;
  P, j, i: integer;

begin
SetLength( result, (Source.Size + 2) div 3 * 4);
Source.Position := 0;
P := 1;
repeat
  BytesRead := Source.Read( ThreeBytes, 3);
  if BytesRead = 0 then break;
  for j := BytesRead to 2 do
    ThreeBytes[j] := 0;
  for j := 0 to BytesRead do
    begin
    result[ P ] := Base64Chars[ ( ThreeBytes[0] shr 2) + 1];
    Inc( P);
    for i := 0 to 1 do
      ThreeBytes[i] := (ThreeBytes[i] shl 6) + (ThreeBytes[i+1] shr 2);
    ThreeBytes[ 2] := ThreeBytes[ 2] shl 6
    end
until BytesRead < 3;
if BytesRead > 0 then
  for j := BytesRead to 2 do
    begin
    result[ P] := '=';
    Inc( P)
    end
end;

内容的提问来源于stack exchange，提问作者David Kroll