RC2键日程表 [英] RC2 key schedule

问题描述

有人可以解释RC2密钥计划如何工作（特别是它的最开始）？我知道它使用小端，但我的实现不工作的任何关键，除了0000 0000 0000 0000

Can someone explain how the RC2 key schedule works (particularly the very beginning of it)? i know it uses little endian, but my implementation is not working for any key except "0000 0000 0000 0000"

Test Vector
Key = 88bc a90e 9087 5a
Plaintext = 0000 0000 0000 0000
Ciphertext = 6ccf 4308 974c 267f

im假设与键相关的第一件事是将其更改为

im assuming that the first thing to do with the key would be to change it into

bc88 0ea9 8790 5a

是的，我知道RC2甚至不再使用，但我仍然想知道

and yes i know RC2 is not even used anymore, but i would still like to know

推荐答案

RFC说：

密钥扩展算法通过将提供的T字节密钥放入密钥缓冲区的字节L [0]，...，L [T-1]开始。

The key expansion algorithm begins by placing the supplied T-byte key into bytes L[0], ..., L[T-1] of the key buffer.

所以如果你的键是 88bc a90e 9087 5a 你会得到 L [0] = 0x88，L [1] = 0xbc，... L [6] = 0x5a 。

So if your key is 88bc a90e 9087 5a you get L[0]=0x88, L[1]=0xbc, ... L[6]=0x5a.

这里不需要考虑任何字节序。

No need to consider any endianess here.

如果你想把密钥缓冲区视为16位字，你可以得到：

If you want to treat the key-buffer as 16-bit words you get:

] = L [2 * i] + 256 * L [2 * i + 1]

K[i] = L[2*i] + 256*L[2*i+1]

K [0] = 0xbc88，K [1] = 0xa90e，K [2] = 0x8790 。 L [7]仅在密钥扩展步骤中稍后分配，因此严格地说，K [3]在此时是未定义的。随意选择任何你想要的值，因为它没有区别的算法。如果选择0，您会得到 K [3] = 0x005a 。

I.e. K[0] = 0xbc88, K[1] = 0xa90e, K[2] = 0x8790. L[7] is only assigned later in the key-expansion step, so strictly speaking K[3] is undefined at this point. Feel free to choose any value you want however, since it makes no difference to the algorithm. If you select 0, you get K[3] = 0x005a.

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