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Comment by userbinator | Hacker News Reader

the static XOR key has been removed from this advisory

...because it's easy enough to determine from the plaintext and ciphertext?

  >>> cb = bytes.fromhex('6968766f606e776c2d2d21262138475c5b5a475b545e475c6b6a776b646e776c6b6a772b646e776c6b6a776b646e776c6b6a776bbadf04036b6a776c616a846f')
  >>> pb = b'\x02\x02\x01\x04\x04\x00\x00\x00FGVMEV0000000000\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00...'
  >>> print(''.join(chr(c ^ k) for c, k in zip(cb, pb)))
 
 kjwkdnwlkjwkdnwlkjwkdnwlkjwkdnwlkjwkdnwlkjYEJ

EDIT: The repeating XOR key is pretty obvious. Just ignore the junk at the end from the `...` in the given plaintext.

Key looks more like they just bashed the home row with a few extensions of the longer fingers.

Apparently, running "uuidgen" is too difficult for them. Which, shouldn't be a surprise for someone who already decided to use XOR "encryption".

Wouldn’t a random sequence using a seed as the secret be a better choice?

That's called a "stream cipher". ;-)

Yes. If you can build a cryptographically-secure random number generator, which can output a long stream of random bytes from a seed, congrats, you just invented a stream cipher. Just XOR your plaintext and random bytes, and you are good to go.

XOR encryption is unbreakable with an one-time pad that matches the message length (that's basically AES CTR). It's one of the most secure cryptography primitives we have.

The problem is deciding to use home-grown encryption.

AES CTR isn't a one-time pad. It's as strong as AES, not theoretically unbreakable.

"Basically" is the key word there.

This isn't a one-time pad. It's reused for every message.

It's reused every 8 bytes...

That too.

I usually say that encryption is the easy part. Just use XOR and you are good. All the complicated bits are related to key management.

Interesting, kjwkdnwl hasn't been seen before in Have I Been Pwned.

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