[英]Decryption from encryption method
I am needing to re-write a decryption method for an old piece of code, unfortunately the original decryption method has been lost on we only have access to the encryption. 我需要为旧代码重新编写一种解密方法,不幸的是,由于我们只能访问加密,因此原来的解密方法已经丢失。
type
TintArray = array [0 .. 1] of Cardinal;
TKeyArray = Array [0 .. 3] of Cardinal;
const
KeyArray: TKeyArray = (858945348, 1144282739, 828794915, 556884274);
procedure Encipher(var V, W: TintArray);
var
y, z, sum, delta, a, b, c, d, n: Cardinal;
iCounter: Integer;
begin
y := V[0];
z := V[1];
sum := 0;
delta := $9E3779B9; // 2654435769;//0x9E3779B9;
a := KeyArray[0];
b := KeyArray[1];
c := KeyArray[2];
d := KeyArray[3];
n := 32;
for iCounter := n downto 1 do begin
sum := sum + delta;
y := y + (((z shl 4) + a) xor (z + sum) xor ((z shr 5) + b));
z := z + (((y shl 4) + c) xor (y + sum) xor ((y shr 5) + d));
end;
W[0] := y;
W[1] := z;
end;
I have tried mundane things like changing all the "+" to "-" however I did not have much hope as I really don't actually understand the code at all. 我已经尝试了一些平凡的事情,例如将所有的“ +”更改为“-”,但是我并不抱有太大希望,因为我实际上根本不了解代码。
This is the Tiny Encryption Algorithm (TEA). 这是微小的加密算法(TEA)。 Check it out on Wikipedia .
在Wikipedia上查看。
Your decryption routine should be something like this (keeping with your naming conventions, etc.): 您的解密例程应该是这样的(遵循您的命名约定等):
procedure Decipher(var V, W: TintArray);
var
y, z, sum, delta, a, b, c, d, n: Cardinal;
iCounter: Integer;
begin
y := V[0];
z := V[1];
sum := $C6EF3720;
delta := $9E3779B9; // 2654435769;//0x9E3779B9;
a := KeyArray[0];
b := KeyArray[1];
c := KeyArray[2];
d := KeyArray[3];
n := 32;
for iCounter := n downto 1 do begin
z := z - (((y shl 4) + c) xor (y + sum) xor ((y shr 5) + d));
y := y - (((z shl 4) + a) xor (z + sum) xor ((z shr 5) + b));
sum := sum - delta;
end;
W[0] := y;
W[1] := z;
end;
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