Cryptographic attacks are methods or techniques by which an intruder exploits the cryptographic system’s weakness to derive the plaintext from the ciphertext, recover the encryption keys, or violate the integrity of the data.
Understanding cryptographic attacks is important in the development of robust security. Different types exist, including brute force, social engineering, rainbow table, known plaintext attack, chosen plaintext attack, chosen ciphertext attack, meet-in-the-middle attack, known key attack, differential cryptanalysis, linear cryptanalysis, implementation attack, side-channel attack, fault injection attack, ransomware attack, birthday attack, and key clustering.
Types of Cryptographic Attacks
1. Brute Force Attack
Brute Force Attack: A cryptanalysis method in which a systematic try of all possible combinations of keys is done until the correct one is hit. This attack is possible since modern computers possess enormous computational powers to take advantage of weak encryption.
Example: An 8-bit-long cipher key would have 28=25628=256 possible combinations. With the use of a program, an attacker can try all possible combinations until he finds the correct key. Although brute force could take an extremely long period of time, the improvement in the processing power of computers has turned brute force attacks into one of the more practical types of attacks against systems that are poorly secured.
2. Social Engineering
Social engineering attacks are a type of attack where attackers manipulate individuals to disclose confidential information or to carry out certain actions that can give them unauthorized access. Unlike other attacks, this attack doesn’t exploit technical vulnerabilities; rather, it’s based on psychological manipulation.
Example: An attacker may send an email phishing from a trusted source, say some bank, requesting the receiver to confirm his/her account information. When the user falls for the deception and provides their credentials, the attacker gains unauthorized access to the account.
3. Rainbow Tables
Rainbow tables are tables precomputed for reversing cryptographic hash functions, which enable an attacker to crack the password in milliseconds. It stores different types of plaintext inputs with their hash values, which enable lookup in no time.
Example: Once the password of a user is hashed and stored in a database, an attacker can find out the plaintext password using a rainbow table by matching the hash value since it is pre-computed. This technique is quite effective for those applications relying on poor passwords.
4. Known Plaintext Attack
The most powerful kind of attack is the known plaintext attack, in which the cryptanalyst has knowledge about both the plaintext and the ciphertext. This information may enable him to deduce either the key or weaknesses of the encryption algorithm.
Example: An intruder may know that a certain message, say “HELLO”, can result in a particular ciphertext. Thus, using the correlation between these two, he could infer the key used, especially for weak encryption techniques.
5. Chosen Plaintext Attack
In a chosen plaintext attack, the attacker gets to arbitrarily choose the plaintext to be encrypted and then gets the corresponding ciphertext. This approach very well serves the purpose of gaining valuable information about the encryption process.
Example: An attacker might submit certain plaintext messages to a system and then observe the respective ciphertexts that come out. Having done this a number of times, one can come up with sufficient information to deduce an encryption key or, in some instances, even take advantage of the weaknesses in the algorithm.
6. Chosen Ciphertext Attack
In the chosen ciphertext attack, the cryptanalyst picks ciphertexts for decryption and gets the respective plaintexts. This may disclose information about the encryption key or the plaintext itself.
For instance, an adversary may submit a manipulated ciphertext to a decryption oracle to reveal the underlying plaintext. In that case, through a sequence of results, the attacker could glean some information about the encryption algorithm or even recover the key.
7. Meet-in-the-Middle Attack
The meet-in-the-middle attack represents one of the cryptanalysis approaches against the class of symmetric key block ciphers. This kind of attack needs precomputation for both encryption and decryption processes and seeks any possible match.
Example: Under a double encryption To encrypt data with two keys. An attacker can encrypt known plaintext with one key and decrypt known ciphertext with the other. A match in the middle could allow an attacker to infer the keys.
8. Known Key Attack
The known key attack involves an attacker having the encryption key in his or her custody and trying to use it to exploit the cryptographic system in such a manner that he or she is able to deduce some plaintext or tamper with data.
Example: Suppose the symmetric encryption algorithm has a key known to an attacker. This attacker would then easily decrypt any ciphertext encrypted under that key, thereby accessing sensitive information.
9. Differential Cryptanalysis
One such method is differential cryptanalysis, which looks at the effect on the resulting difference at the output, given a difference in input. It turns out, quite surprisingly, to be very effective against block ciphers.
Example: Suppose an attacker encrypts two plaintexts that differ by some known value and analyzes how the differential information travels through the encryption process. Normally, such an analysis of output differences informs the attacker about something of the key used.
10. Linear Cryptanalysis
Linear cryptanalysis is a statistical approach to find the linear approximations of the behavior of a cipher. It can be used to recover keys from block ciphers.
Example: An attacker may analyze the dependence between plaintexts, ciphertexts and a key to establish linear equations. The attacker can find the key by collecting sufficient data in order to solve such equations.
11. Implementation Attacks
Implementation attacks, on the other hand, enable the attackers to break cryptographic schemes due to errors in implementation rather than those in the cryptographic algorithms themselves. They could be based on software bugs, misconfiguration, or insecure coding practices.
Example: An intruder may exploit a buffer overflow in a cryptographic library to execute arbitrary code. That would be proof that secure coding and testing are very important.
12. Side-Channel Attacks
Side-channel attacks take their information from the physical implementation of a cryptographic engine, such as timing information, power consumption, or electromagnetic leaks. Side-channel attacks potentially reveal every detail of an encryption key.
Example: A timing attack uses the different execution times of various operations in a cryptographic algorithm. The attacker can measure the differences in time and deduce information on the key used.
13. Fault Injection Attacks
Fault injection attacks form a category of attacks that exploit the introduction of errors into a cryptographic system in order to observe the behavior of the latter in the case of their occurrence. In such a way, vulnerabilities might be revealed that eventually could be utilized.
Example: An attacker provokes a fault in a cryptographic chip. Afterward, the chip generates faulty outputs. These could provide, following an analysis, valuable information on the inside state of the system and probably lead to the restoration of the encryption key.
14. Ransomware
Ransomware is a malware that encrypts the victim’s files and asks for payment for the key needed to decrypt the data. It’s an attack on the particular dependence of the victim on data, thus causing great financial and operational damage.
Example: The WannaCry ransomware attack in 2017 encrypted the files of thousands of organizations around the world and asked for ransom in Bitcoin. This attack initiated regular backups and effective security measures.
15. Birthday Attack
The birthday attack is a method of exploiting the mathematics of the birthday paradox: given a group of people, if enough people are added to the group, then there is a probability that two persons sharing the same birthday will occur. In cryptographic attacks, it targets hash functions.
Example: An attacker might generate a number of inputs in the hope that two different inputs will result in the same hash value. A collision like this can be used to break systems relying on the hash function for their security, such as digital signatures.
16. Key Clustering
Whenever multiple keys on one input produce the same output, this is considered key clustering, posing a weakness in cryptograms. This will weaken the security of key management and encrypting processes.
That would mean that, for the same plaintext, if two different keys result in obtaining the same ciphertext, then an intruder can take advantage of such a relation in order to find an original key or somehow influence the system.
Conclusion
The most salient attacks against sensitive information and systems are brute force, social engineering, rainbow tables, and other cryptanalytic attacks. Understanding such threats will provide ways in which effective countermeasures can be devised. Subsequently, an organization will be able to improve defenses against such attacks by deploying good security practices, refreshing cryptographic protocols from time to time, and educating users about the potential threats.