BUYING Looking for broken decryptor help or wlakthrough
by orwell1984 - February 14, 2021 at 08:00 PM
#1
Hi, I'm looking for help solving broken decryptor or walkthrough. I can buy or give credits or maybe trade if i have something you want.
#2
The OTP has omitted 1 specific byte that will never allow a plaintext byte to encrypt to itself, you can utilize this to attack :-)
#3
(February 15, 2021 at 10:48 AM)thebigbad Wrote: The OTP has omitted 1 specific byte that will never allow a plaintext byte to encrypt to itself, you can utilize this to attack :-)

Thanks for the tip, I'll look into it although I'm not sure how to leverage that...
#4
(February 15, 2021 at 10:48 AM)thebigbad Wrote: The OTP has omitted 1 specific byte that will never allow a plaintext byte to encrypt to itself, you can utilize this to attack :-)

it's a type attack bitflip attack?
#5
If the OTP can never contain a null byte, that means that the plaintext can never be encrypted to itself.

So you want to keep requesting the flag, and keep a count of which bytes you see for each position, until you have seen all but 1 byte for each position. You do the same by encrypting a lot of 00's.

It will take like 10k requests, but then you have the key and the encrypted flag, since the AES mode is basically a stream cipher you can just XOR those two.
#6
(February 16, 2021 at 11:08 AM)thebigbad Wrote: If the OTP can never containĀ  a null byte, that means that the plaintext can never be encrypted to itself.

So you want to keep requesting the flag, and keep a count of which bytes you see for each position, until you have seen all but 1 byte for each position. You do the same by encrypting a lot of 00's.

It will take like 10k requests, but then you have the key and the encrypted flag, since the AES mode is basically a stream cipher you can just XOR those two.

Thank you so much, finally got it

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