Difference between revisions of "Talk:153: Cryptography"
BinaryDigit (talk | contribs) (Feistel networks do not require a reverse of the encryption function, only of the key schedule.) |
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''In the same way, a steps to a feistel cipher based algorithm are executed in reverse to obtain the original plain text from a cipher text.'' is not true. The whole point of a Feistel network is that you execute the same steps ''in the same order''. The only thing that is reversed is the key. You can do almost any amount of mangling of the input, without having to worry about how to reverse it, because the magic of XOR ensures that All Will Be Well when you come to decrypt. There are limits to the kinds of mangling you can do, of course, but the basic principle is that the same function used for encryption is also used for decryption. It's quite startling, really. Horst Feistel - kudos! | ''In the same way, a steps to a feistel cipher based algorithm are executed in reverse to obtain the original plain text from a cipher text.'' is not true. The whole point of a Feistel network is that you execute the same steps ''in the same order''. The only thing that is reversed is the key. You can do almost any amount of mangling of the input, without having to worry about how to reverse it, because the magic of XOR ensures that All Will Be Well when you come to decrypt. There are limits to the kinds of mangling you can do, of course, but the basic principle is that the same function used for encryption is also used for decryption. It's quite startling, really. Horst Feistel - kudos! | ||
| + | --[[User:BinaryDigit|BinaryDigit]] ([[User talk:BinaryDigit|talk]]) 15:08, 8 August 2014 (UTC) | ||
Revision as of 15:08, 8 August 2014
I think that executing that S-box twice would get you back where you started. gijobarts (talk) 05:28, 30 July 2013 (UTC)
- Actually that's not true. Regardless of the bit in position 1 to begin with, you will always have a 1 in position 8 in the result. When you shift, you're adding a 0 in position 1 (assuming a 0 shift in), then the inverse is 1, and flipping would put the 1 in position 8. Jarod997 (talk) 14:06, 5 March 2014 (UTC)
" and so is the author Randall Munroe at PyCon"
- I think that post is a joke.
- It links to 541: TED Talk.
- It says "Registration volunteers have been instructed to refuse admission to Randall Munroe personally, and in fact, to any stick figures who may attempt to register"
- There isn't anything on YouTube or Randall Munroe's Wikipedia page about it.
- Another Python blog says that it was a publicity stunt, citing the organizers' mailing list archives. I didn't bother to sign up for access to the archive.
- Catherine Devlin claims that she banned Randall, so we could try asking her if she's serious.
- Another blog post about it
- gijobarts (talk) 16:48, 2 September 2013 (UTC) (edited 20:29 UTC)
In the same way, a steps to a feistel cipher based algorithm are executed in reverse to obtain the original plain text from a cipher text. is not true. The whole point of a Feistel network is that you execute the same steps in the same order. The only thing that is reversed is the key. You can do almost any amount of mangling of the input, without having to worry about how to reverse it, because the magic of XOR ensures that All Will Be Well when you come to decrypt. There are limits to the kinds of mangling you can do, of course, but the basic principle is that the same function used for encryption is also used for decryption. It's quite startling, really. Horst Feistel - kudos! --BinaryDigit (talk) 15:08, 8 August 2014 (UTC)
