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The OAEP algorithm is a form of Feistel network which uses a pair of random oracles G and H to process the plaintext prior to asymmetric encryption. When combined with any secure trapdoor one-way permutation f {\displaystyle f} , this processing is proved in the random oracle model to result in a combined scheme which is semantically secure ...
In cryptography, a padding oracle attack is an attack which uses the padding validation of a cryptographic message to decrypt the ciphertext. In cryptography, variable-length plaintext messages often have to be padded (expanded) to be compatible with the underlying cryptographic primitive.
In cryptography, padding is any of a number of distinct practices which all include adding data to the beginning, middle, or end of a message prior to encryption. In classical cryptography, padding may include adding nonsense phrases to a message to obscure the fact that many messages end in predictable ways, e.g. sincerely yours.
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:
A key encapsulation mechanism, to securely transport a secret key from a sender to a receiver, consists of three algorithms: Gen, Encap, and Decap. Circles shaded blue—the receiver's public key and the encapsulation —can be safely revealed to an adversary, while boxes shaded red—the receiver's private key and the encapsulated secret key —must be kept secret.
A chosen-ciphertext attack (CCA) is an attack model for cryptanalysis where the cryptanalyst can gather information by obtaining the decryptions of chosen ciphertexts. From these pieces of information the adversary can attempt to recover the secret key used for decryption.
For an asymmetric key encryption algorithm cryptosystem to be semantically secure, it must be infeasible for a computationally bounded adversary to derive significant information about a message (plaintext) when given only its ciphertext and the corresponding public encryption key. Semantic security considers only the case of a "passive ...
where A S(k, · ) denotes that A has access to the oracle S(k, · ), and Query(A S(k, · ), 1 n) denotes the set of the queries on S made by A, which knows n. Clearly we require that any adversary cannot directly query the string x on S, since otherwise a valid tag can be easily obtained by that adversary. [6]