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93 lines
3.4 KiB
PHTML
93 lines
3.4 KiB
PHTML
(*************************************************************************
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Include file for AES_DECR.PAS - AES_Decrypt for Pascal16/Full tables
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Version Date Author Modification
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------- -------- ------- ------------------------------------------
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0.10 09.07.06 W.Ehrhardt Initial version from AES_DECR.PAS
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0.11 15.11.08 we Use Ptr2Inc from BTypes
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**************************************************************************)
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(**** (C) Copyright 2002-2008 Wolfgang Ehrhardt -- see copying_we.txt ****)
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{Normally used for TP5/5.5 (and during development BP7)}
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{---------------------------------------------------------------------------}
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procedure AES_Decrypt(var ctx: TAESContext; {$ifdef CONST} const {$else} var {$endif} BI: TAESBlock; var BO: TAESBlock);
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{-decrypt one block (in ECB mode)}
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label done;
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var
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r: integer;
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pK: PWA4; {pointer to loop rount key }
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s,t: TAESBlock;
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begin
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{Setup key pointer}
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pK := PWA4(@ctx.RK[ctx.Rounds]);
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{Initialize with input block}
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TWA4(s)[0] := TWA4(BI)[0] xor pK^[0];
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TWA4(s)[1] := TWA4(BI)[1] xor pK^[1];
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TWA4(s)[2] := TWA4(BI)[2] xor pK^[2];
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TWA4(s)[3] := TWA4(BI)[3] xor pK^[3];
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dec(Ptr2Inc(pK), 4*sizeof(longint));
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r := ctx.Rounds-1;
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while true do begin
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TWA4(t)[3] := Td0[s[3*4+0]] xor Td1[s[2*4+1]] xor Td2[s[1*4+2]] xor Td3[s[0*4+3]] xor pK^[3];
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TWA4(t)[2] := Td0[s[2*4+0]] xor Td1[s[1*4+1]] xor Td2[s[0*4+2]] xor Td3[s[3*4+3]] xor pK^[2];
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TWA4(t)[1] := Td0[s[1*4+0]] xor Td1[s[0*4+1]] xor Td2[s[3*4+2]] xor Td3[s[2*4+3]] xor pK^[1];
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TWA4(t)[0] := Td0[s[0*4+0]] xor Td1[s[3*4+1]] xor Td2[s[2*4+2]] xor Td3[s[1*4+3]] xor pK^[0];
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dec(Ptr2Inc(pK), 4*sizeof(longint));
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dec(r);
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if r<1 then goto done;
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TWA4(s)[3] := Td0[t[3*4+0]] xor Td1[t[2*4+1]] xor Td2[t[1*4+2]] xor Td3[t[0*4+3]] xor pK^[3];
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TWA4(s)[2] := Td0[t[2*4+0]] xor Td1[t[1*4+1]] xor Td2[t[0*4+2]] xor Td3[t[3*4+3]] xor pK^[2];
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TWA4(s)[1] := Td0[t[1*4+0]] xor Td1[t[0*4+1]] xor Td2[t[3*4+2]] xor Td3[t[2*4+3]] xor pK^[1];
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TWA4(s)[0] := Td0[t[0*4+0]] xor Td1[t[3*4+1]] xor Td2[t[2*4+2]] xor Td3[t[1*4+3]] xor pK^[0];
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dec(Ptr2Inc(pK), 4*sizeof(longint));
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dec(r);
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end;
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done:
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s[00] := InvSBox[t[0*4+0]];
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s[01] := InvSBox[t[3*4+1]];
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s[02] := InvSBox[t[2*4+2]];
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s[03] := InvSBox[t[1*4+3]];
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s[04] := InvSBox[t[1*4+0]];
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s[05] := InvSBox[t[0*4+1]];
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s[06] := InvSBox[t[3*4+2]];
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s[07] := InvSBox[t[2*4+3]];
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s[08] := InvSBox[t[2*4+0]];
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s[09] := InvSBox[t[1*4+1]];
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s[10] := InvSBox[t[0*4+2]];
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s[11] := InvSBox[t[3*4+3]];
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s[12] := InvSBox[t[3*4+0]];
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s[13] := InvSBox[t[2*4+1]];
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s[14] := InvSBox[t[1*4+2]];
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s[15] := InvSBox[t[0*4+3]];
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TWA4(BO)[0] := TWA4(s)[0] xor pK^[0];
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TWA4(BO)[1] := TWA4(s)[1] xor pK^[1];
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TWA4(BO)[2] := TWA4(s)[2] xor pK^[2];
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TWA4(BO)[3] := TWA4(s)[3] xor pK^[3];
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end;
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{---------------------------------------------------------------------------}
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procedure MakeDecrKey(var ctx: TAESContext);
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{-Calculate decryption key from encryption key}
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var
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i: integer;
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x: longint;
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t: TBA4 absolute x;
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begin
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with ctx do begin
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for i:=4 to 4*Rounds-1 do begin
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{Inverse MixColumns transformation: use Sbox and}
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{implicit endian conversion compared with [2] }
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x := TAWK(RK)[i];
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TAWK(RK)[i] := Td3[SBox[t[3]]] xor Td2[SBox[t[2]]] xor Td1[SBox[t[1]]] xor Td0[SBox[t[0]]];
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end;
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end;
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end;
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