By Michael Scott
Understanding a Known-Plaintext Attack
The attack occurs when the perpetrator accesses the encrypted data (ciphertext) besides the original unencrypted version identified as plaintext. The attacker attempts to discover the encryption key or method by comparing the two.
For instance, in case the word ‘blockchain’ is encrypted as ‘eyrtnxkelm,’ knowing the pair could enable the attacker to decode other constituents of the message that utilize the same key. This illustrates how, in some encryption methods, even a small amount of data can aid in breaking the encryption.
The attacker leverages weaknesses in encryption tactics, permitting attackers to recognize trends or relationships between the plaintext and ciphertext. Lack of proper protection can result in known-plaintext attacks undermining an encryption system’s security.
The two techniques utilized to exploit plaintext and ciphertext include:
- Pattern matching: Bad actors search for repeating patterns. In case the same plaintext leads to the same ciphertext, they can recognize trends in the encrypted text and utilize them to decipher the encryption algorithm, finally decrypting the whole message.
- Frequent analysis: Attackers utilize simple encryption tactics where every symbol or letter is replaced with a specific one. A comparison of the frequency of patterns or letters in the plaintext or ciphertext can enable attackers to uncover the key or decode the rest of the message.
How a Known-Plaintext Attack Works
Using the previous ‘blockchain’ and ‘eorfhfkdlq’ example, the attack might work in the following ways:
Step 1: Attackers gather pairs of plaintexts and their corresponding ciphertexts. Data leaks and intercepted communications are examples of ways in which they can be acquired.
Step 2: The letters in the plaintext to the corresponding letters in the ciphertext are compared. Studying how every letter in the plaintext changes into a different letter in the ciphertext can enable the attacker to identify a trend.
Step 3: The attacker can rely on changes between the plaintext to make informed guesses concerning the encrypted algorithms. For instance, in case the letters are shifted by a fixed number of positions, the attacker may notice that each letter in the ‘blockchain’ has been shifted by a specific number of places in the alphabet.
Step 4: After the attacker identifies the encryption rule or pattern, they can utilize that knowledge to decrypt other parts of the message or future messages that utilize the same algorithm or key.
Chosen-Plaintext Attacks Versus Known-Plaintext Attacks
Chosen-plaintext attacks (CPA): Attackers can pick or choose the plaintext they desire and study how it is encrypted into ciphertext.
Known-plaintext attacks (KPA): Attackers already have access to some plaintext-ciphertext pairs and utilize this information to evaluate the encryption without picking out the plaintext themselves. A proper understanding of the differences is vital for creating robust cryptographic defenses.
How to Protect Against a Known-Plaintext Attack
One should pick encryption algorithms capable of withstanding known-plaintext attacks by utilizing robust encryption tactics. By averting patterns in the plaintext from correlating with patterns in the ciphertext, modern cryptographic algorithms such as the Advanced Encryption Standard (AES) are made to survive such attacks. AES is a vastly utilized symmetric encryption algorithm famous for its efficacy and security.
People should also manage encryption keys securely to avert unapproved access. This entails using secure key repositories, rotating keys regularly, and utilizing robust key generation techniques.
It is also crucial to avoid encrypting discrete, predictable data chunks. The entire message or file should be encrypted to prevent an attacker from utilizing known pairs.
Using different keys for different sessions and endeavors is crucial. The effect of a known-plaintext attack is reduced since every session will utilize a unique encryption key.
It is also important to maintain the most recent version of libraries, systems, and encryption software. Security fixes that address susceptibilities are regularly included in updates.
Prior to encrypting the data’s plaintext, a cryptographic salt must be added. This makes every transaction special, even when encrypting the same plaintext several times.
People should avoid encryption methods that are susceptible to known-plaintext attacks. Finally, exercising caution is critical when identifying the encryption algorithms.