Cryptography Tricks: Difference between revisions
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* If cbc is used on a block and if the attacker knows where 16 bytes of zeroes are located in known plaintext with given ciphertext location, he can use AES-ECB with the guessed key on that location. if there is a match of the previous 16 bytes as result, the attacker automatically knows the guessed key is the correct key | * If cbc is used on a block and if the attacker knows where 16 bytes of zeroes are located in known plaintext with given ciphertext location, he can use AES-ECB with the guessed key on that location. if there is a match of the previous 16 bytes as result, the attacker automatically knows the guessed key is the correct key | ||
* this means that the first 0x10 bytes of the ciphered text will be equal to the second 0x10 bytes of the plaintext, if the plaintext is supposed to have zeroes in the cbc decryption. | * this means that the first 0x10 bytes of the ciphered text will be equal to the second 0x10 bytes of the plaintext of the ecb decryption, if the plaintext is supposed to have zeroes in the cbc decryption and the ecb/cbc key is correct. | ||
{{Reverse engineering}}<noinclude>[[Category:Main]]</noinclude> | {{Reverse engineering}}<noinclude>[[Category:Main]]</noinclude> | ||
Revision as of 02:10, 20 August 2021
Here are some cryptography tricks that i've learned with some important people and that helped made this page. They helped a lot with the Keys and Seeds page construction. Use them wisely :)
AES-CTR tricks
- Recovery of partial plaintext with two ciphertexts encrypted with same key and iv by knowing where zeroes (\x00) are located
- This trick was used in the recovery of the ebootrom keys
- Xoring these ciphertexts will reveal plaintext where in both locations there are zeroes in one place and plaintext in the other
AES-CBC tricks
- The iv of a CBC operation is always the previous 0x10 block, UNLESS it's the starting operation. in this case it is specified by the end-user
AES-ECB tricks
- If cbc is used on a block and if the attacker knows where 16 bytes of zeroes are located in known plaintext with given ciphertext location, he can use AES-ECB with the guessed key on that location. if there is a match of the previous 16 bytes as result, the attacker automatically knows the guessed key is the correct key
- this means that the first 0x10 bytes of the ciphered text will be equal to the second 0x10 bytes of the plaintext of the ecb decryption, if the plaintext is supposed to have zeroes in the cbc decryption and the ecb/cbc key is correct.
