A cryptographic primitive is a type of cryptographic algorithm: a small, useful building block that provides a security function and can be combined with others to build protocols. Encryption, hashing, and digital signatures are examples of the broader idea; symmetric encryption is a primitive, while AES is a specific algorithm that instantiates it. section 1.9 section 1.2
Primitives are commonly understood through several useful distinctions:
- Symmetric primitives use one secret key; asymmetric primitives use different keys or give participants different views of key material. section 1.5 section 1.4
- Some constructions rely on mathematical problems, while others use heuristic designs supported by observation and cryptanalysis; the former are often slower. section 1.5
- Security claims commonly target confidentiality, authentication, or both, but each primitive must be understood as a tool with a particular claim. section 1.5 section 1.9
A message becomes noise
Alice and Bob first agree on a secret key. Alice applies ENCRYPT to her message and the key, sending Bob an apparently random encrypted message. Bob applies DECRYPT with the same key and recovers the original message; an observing messenger should learn nothing about its contents. section 1.2
Primitives do not secure a system by themselves. Real protocols combine them like Lego, and misuse or unsafe combinations can create vulnerabilities. Prefer respected, standardized implementations, read their usage requirements, and avoid inventing or assembling cryptography casually. section 16.1 section 16.8
Figure 1.4 The cryptographic algorithms you have learned so far. AES is an instantiation of a symmetric encryption algorithm, which is a cryptographic primitive that is part of the broader class of symmetric cryptographic algorithms.
Use the classification diagram to place AES as a specific symmetric-encryption algorithm, a primitive within the broader family of symmetric cryptography. section 1.3
