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Include file for AES_DECR.PAS - AES_Decrypt for Pascal16/Compressed tables
Version Date Author Modification
------- -------- ------- ------------------------------------------
0.10 09.07.06 W.Ehrhardt Initial version for compressed tables
0.11 13.07.06 we Uses TDe box byte instead of InvSBox
0.12 15.11.08 we Use Ptr2Inc from BTypes
(**** (C) Copyright 2002-2008 Wolfgang Ehrhardt -- see copying_we.txt ****)
{Normally used for TP5/5.5 (and during development BP7)}
procedure AES_Decrypt(var ctx: TAESContext; {$ifdef CONST} const {$else} var {$endif} BI: TAESBlock; var BO: TAESBlock);
{-decrypt one block (in ECB mode)}
label done;
r: integer;
pK: PWA4; {pointer to loop rount key }
s,t: TAESBlock;
{Setup key pointer}
pK := PWA4(@ctx.RK[ctx.Rounds]);
{Initialize with input block}
TWA4(s)[0] := TWA4(BI)[0] xor pK^[0];
TWA4(s)[1] := TWA4(BI)[1] xor pK^[1];
TWA4(s)[2] := TWA4(BI)[2] xor pK^[2];
TWA4(s)[3] := TWA4(BI)[3] xor pK^[3];
dec(Ptr2Inc(pK), 4*sizeof(longint));
r := ctx.Rounds-1;
while true do begin
TWA4(t)[3] := Td[s[3*4+0]].D0.L xor Td[s[2*4+1]].D1.L xor Td[s[1*4+2]].D2.L xor Td[s[0*4+3]].D3.L xor pK^[3];
TWA4(t)[2] := Td[s[2*4+0]].D0.L xor Td[s[1*4+1]].D1.L xor Td[s[0*4+2]].D2.L xor Td[s[3*4+3]].D3.L xor pK^[2];
TWA4(t)[1] := Td[s[1*4+0]].D0.L xor Td[s[0*4+1]].D1.L xor Td[s[3*4+2]].D2.L xor Td[s[2*4+3]].D3.L xor pK^[1];
TWA4(t)[0] := Td[s[0*4+0]].D0.L xor Td[s[3*4+1]].D1.L xor Td[s[2*4+2]].D2.L xor Td[s[1*4+3]].D3.L xor pK^[0];
dec(Ptr2Inc(pK), 4*sizeof(longint));
if r<1 then goto done;
TWA4(s)[3] := Td[t[3*4+0]].D0.L xor Td[t[2*4+1]].D1.L xor Td[t[1*4+2]].D2.L xor Td[t[0*4+3]].D3.L xor pK^[3];
TWA4(s)[2] := Td[t[2*4+0]].D0.L xor Td[t[1*4+1]].D1.L xor Td[t[0*4+2]].D2.L xor Td[t[3*4+3]].D3.L xor pK^[2];
TWA4(s)[1] := Td[t[1*4+0]].D0.L xor Td[t[0*4+1]].D1.L xor Td[t[3*4+2]].D2.L xor Td[t[2*4+3]].D3.L xor pK^[1];
TWA4(s)[0] := Td[t[0*4+0]].D0.L xor Td[t[3*4+1]].D1.L xor Td[t[2*4+2]].D2.L xor Td[t[1*4+3]].D3.L xor pK^[0];
dec(Ptr2Inc(pK), 4*sizeof(longint));
s[00] := Td[t[0*4+0]].D0.box;
s[01] := Td[t[3*4+1]].D0.box;
s[02] := Td[t[2*4+2]].D0.box;
s[03] := Td[t[1*4+3]].D0.box;
s[04] := Td[t[1*4+0]].D0.box;
s[05] := Td[t[0*4+1]].D0.box;
s[06] := Td[t[3*4+2]].D0.box;
s[07] := Td[t[2*4+3]].D0.box;
s[08] := Td[t[2*4+0]].D0.box;
s[09] := Td[t[1*4+1]].D0.box;
s[10] := Td[t[0*4+2]].D0.box;
s[11] := Td[t[3*4+3]].D0.box;
s[12] := Td[t[3*4+0]].D0.box;
s[13] := Td[t[2*4+1]].D0.box;
s[14] := Td[t[1*4+2]].D0.box;
s[15] := Td[t[0*4+3]].D0.box;
TWA4(BO)[0] := TWA4(s)[0] xor pK^[0];
TWA4(BO)[1] := TWA4(s)[1] xor pK^[1];
TWA4(BO)[2] := TWA4(s)[2] xor pK^[2];
TWA4(BO)[3] := TWA4(s)[3] xor pK^[3];
procedure MakeDecrKey(var ctx: TAESContext);
{-Calculate decryption key from encryption key}
i: integer;
x: longint;
t: TBA4 absolute x;
with ctx do begin
for i:=4 to 4*Rounds-1 do begin
{Inverse MixColumns transformation: use Sbox and}
{implicit endian conversion compared with [2] }
x := TAWK(RK)[i];
TAWK(RK)[i] := Td[SBox[t[3]]].D3.L xor Td[SBox[t[2]]].D2.L xor Td[SBox[t[1]]].D1.L xor Td[SBox[t[0]]].D0.L;