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Understanding Deterministic Random Bit Generator (DRBG)

CryptographyDRBGSecurity NotionsIND-CPARandom Bit Generation

A Deterministic Random Bit Generator (DRBG) is an algorithm that produces bits that appear random, derived from a secret value known as a seed. This algorithm is crucial in cryptographic systems for generating randomness.

Key Points

  • DRBG Algorithm: The DRBG algorithm generates random bits from a seed.
  • Encryption Method: The encryption method E is defined as: 
    E(K, R, P) = (DRBG(K || R) ⊕ P, R)
    where R is a randomly chosen value for each call to E, and K || R denotes the concatenation of K and R.

Security Notions

IND-CPA

  • IND-CPA: A security notion combining indistinguishability (IND) with a chosen-plaintext attack (CPA) model.
  • CPA: A model of attack where the attacker can choose plaintexts to be encrypted.
  • IND: An objective of security where the attacker cannot distinguish between encryptions of different messages.

Breakdown of Terms

Indistinguishability (IND)

  • IND: Ensures that an attacker cannot distinguish between encryptions of different messages.

Chosen-Plaintext Attack (CPA)

  • CPA: Allows the attacker to choose plaintexts to be encrypted, testing the encryption system's robustness.

Combining Security Objectives and Attack Models

A security notion is obtained by combining a security objective with an attack model. For example, IND-CPA combines the security objective of indistinguishability with the chosen-plaintext attack model.

Learn More

For a deeper understanding of DRBG and its applications in cryptography, consider exploring resources on cryptographic algorithms and security notions.