Cryptanalysis is the study of analyzing information. The technique is put to use to break through cryptographic security systems and gain entry into the contents of encrypted messages, even if the cryptographic key is unknown.
Apart from mathematical analysis of cryptographic algorithms, cryptanalysis also incorporates the study of side-channel attacks that do not focus on weaknesses in the cryptographic algorithms themselves, but instead make use of weaknesses in their application.
Information Available to Attackers:
Attacks are based on the type of information the attacker can avail. Countless examples of secret algorithms falling prey to wider knowledge are scattered throughout history. Mentioned below are a few examples:
- Ciphertext-only. The cryptanalyst has access to a finite amount of cipher texts or code texts
- Known-plaintext. The corresponding plaintexts for the cipher texts is known to the cryptanalyst
- Related-key attack. The attacker can obtain encrypted under two different keys. The keys are unknown however, their relationship is known. For example, two keys that differ in one bit.
Utilization of Computational Resources:
Characterization of attacks is based on the requirement of their resources. These are:
- Time- The number of test encryptions that must be done
- Data- Type of plaintexts and cipher texts needed for a specific approach, including its quantity
- Memory- Storage required to initiate the attack
It is troublesome to predict these quantities precisely; however, the estimated “order of magnitude” of their attacks’ difficulty is given.
The Wonderful World of Algorithms 