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An attack called POODLE [19] (late 2014) combines both a downgrade attack (to SSL 3.0) with a padding oracle attack on the older, insecure protocol to enable compromise of the transmitted data. In May 2016 it has been revealed in CVE-2016-2107 that the fix against Lucky Thirteen in OpenSSL introduced another timing-based padding oracle. [20] [21]
The attacker can then combine the oracle with a systematic search of the problem space to complete their attack. [1] The padding oracle attack, and compression oracle attacks such as BREACH, are examples of oracle attacks, as was the practice of "crib-dragging" in the cryptanalysis of the Enigma machine. An oracle need not be 100% accurate ...
It is a new variant of Serge Vaudenay's padding oracle attack that was previously thought to have been fixed, that uses a timing side-channel attack against the message authentication code (MAC) check stage in the TLS algorithm to break the algorithm in a way that was not fixed by previous attempts to mitigate Vaudenay's attack.
The attack uses the padding as an oracle. [4] [5] PKCS #1 was subsequently updated in the release 2.0 and patches were issued to users wishing to continue using the old version of the standard. [3] However, the vulnerable padding scheme remains in use and has resulted in subsequent attacks:
In cryptography, Optimal Asymmetric Encryption Padding (OAEP) is a padding scheme often used together with RSA encryption. OAEP was introduced by Bellare and Rogaway , [ 1 ] and subsequently standardized in PKCS#1 v2 and RFC 2437.
A block cipher consists of two paired algorithms, one for encryption, E, and the other for decryption, D. [1] Both algorithms accept two inputs: an input block of size n bits and a key of size k bits; and both yield an n-bit output block. The decryption algorithm D is defined to be the inverse function of encryption, i.e., D = E −1.
POODLE (which stands for "Padding Oracle On Downgraded Legacy Encryption") is a security vulnerability which takes advantage of the fallback to SSL 3.0. [1] [2] [3] If attackers successfully exploit this vulnerability, on average, they only need to make 256 SSL 3.0 requests to reveal one byte of encrypted messages.
Padding oracle attacks can be avoided by making sure that an attacker cannot gain knowledge about the removal of the padding bytes. This can be accomplished by verifying a message authentication code (MAC) or digital signature before removal of the padding bytes, or by switching to a streaming mode of operation.