Malleability definition
Malleability is the property of certain data or cryptographic elements (e.g., encrypted messages or digital signatures) to be modified by an unauthorized entity without changing the underlying data.
Malleability poses a significant security risk as it could allow attackers to tamper with data and potentially exploit vulnerabilities or create fraudulent transactions without being detected easily. It is crucial to address and mitigate malleability issues to ensure the integrity and trustworthiness of digital communications and systems.
See also: encryption key
How malleability works
- When encrypted, data transforms into a format that appears gibberish without the proper decryption key.
- In some encryption schemes, certain ciphertext modifications can occur without altering the underlying data. For example, an attacker might intercept the message, then change specific bits or blocks of the encrypted message without knowing the decryption key. They will have modified the ciphertext.
- The decryption process might still produce meaningful but altered plaintext, which could be a security concern.
Malleable encryption modes
- Cipher Block Chaining (CBC) is susceptible to this issue. In CBC, each plaintext block is encrypted separately, and the result of the previous block is used to encrypt the next block. This chaining of blocks can lead to malleability.
- Cipher Feedback (CFB) mode turns a block cipher into a self-synchronizing stream cipher. It allows for feedback from previous ciphertext blocks to the encryption process. This feedback mechanism can introduce malleability in specific scenarios.
- Output Feedback (OFB) mode transforms a block cipher into a synchronous stream cipher. Like CFB, it uses feedback from previous ciphertext blocks, which could introduce malleability.
How hackers may use malleability
- Ransomware attacks
- Replay attacks
- Malicious modifications in encrypted databases
- Padding oracle attacks
- Message alteration in secure communication
