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An attacker may use XML injection to perform the equivalent of a XSS, in which requesters of a valid Web service have their requests transparently rerouted to an attacker-controlled Web service that performs malicious operations.

Cryptanalysis

The operations performed in defeating cryptographic protection without an initial knowledge of the key employed in providing the protection.

Cryptanalytic attacks

Several attacks such as COA, KPA, CTA, CPA, ACPA, CCA, and ACCA are possible as follows.

Ciphertext only attack (COA): An attacker has some ciphertext and he does not know the plaintext or the key. His goal is to find the corresponding plaintext. This is the most common attack and the easiest to defend because the attacker has the least amount of information (i.e., ciphertext only) to work with.

Known plaintext attack (KPA): An attacker is able to match the ciphertext with the known plaintext and the encryption algorithm but does not know the key to decode the ciphertext. This attack is harder, but still common because the attacker tries to deduce the key based on the known plaintext. This attack is similar to brute force attack. The KPA works against data encryption standard (DES) in any of its four operating modes (i.e., ECB, CBC, CFB, and OFB) with the same complexity. DES with any number of rounds fewer than 16 could be broken with a known-plaintext attack more efficiently than by brute force attack.

Chosen text attack (CTA): Less common in occurrence and includes four types of attacks such as CPA, ACPA, CCA, and ACCA.

Chosen plaintext attack (CPA): The attacker knows the plaintext and the corresponding ciphertext and algorithm, but does not know the key. He has selected the plaintext together with its corresponding encrypted ciphertext generated with the secret key. This type of attack is harder but still possible. The CPA attack occurs when a private key is used to decrypt a message. The key is deduced to decrypt any new messages encrypted with the same key. A countermeasure is to use a one-way hash function. The CPA attack against DES occurs when bit-wise complement keys are used to encrypt the complement of the plaintext block into the complement of the ciphertext block. A solution is to not use the complement keys.

Adaptive CPA attack (ACPA): A variation of the CPA attack where the selection of the plaintext is changed based on the previous attack results.

Chosen ciphertext attack (CCA): The attacker selected the ciphertext together with its corresponding decrypted plaintext generated with the secret key.

Adaptive CCA attack (ACCA): A variation of the CCA attack where the selection of the ciphertext is changed based on the previous attack results.

Cryptographic algorithm

A well-defined computational procedure that takes variable inputs, including a cryptographic key, and produces an output. The cryptographic algorithms can be implemented in either hardware for speed or software for flexibility.

Cryptographic boundary

An explicitly defined continuous perimeter that establishes the physical bounds of a cryptographic module and contains all the hardware, software, and/or firmware components of a cryptographic module.

Cryptographic authentication

The use of encryption-related techniques to provide authentication.

Cryptographic checksum

A checksum computed by an algorithm that provides a unique value for each possible data value of the object.

Cryptographic function

A set of mathematical procedures that provide various algorithms for key generation, random number generation, encryption, decryption, and message digesting.

Cryptographic hash function

A mathematical function that maps a bit string of arbitrary length to a fixed length bit string. The function satisfies the following properties: (1) it is computationally infeasible to find any input which maps to any pre-specified output (one-way) and (2) it is computationally infeasible to find any two distinct inputs that map to the same output (collision collision-resistant).

Cryptographic key