Cryptography is the science of protecting information by converting readable data into a form that stays unintelligible to anyone without the correct key. Modern schemes lean on mathematical problems that are impractical to reverse without that key, such as factoring the product of two large primes in the algorithm behind RSA.
The discipline delivers four services that surface again and again in practice: confidentiality, integrity, authentication, and non-repudiation. A digital signature, for example, proves who sent a message and confirms nobody altered it along the way. Here is a piece of hard-won advice worth remembering. Never invent your own algorithm. Security should rest on the secrecy of the key, not the obscurity of the method, a principle that trips up people who assume a hidden algorithm is automatically a strong one.
How is cryptography tested on the CISSP?
Cryptography gets heavy coverage in Domain 3: Security Architecture and Engineering. You need to separate symmetric from asymmetric systems, reason about key management across a key’s full life, recognize algorithms like AES and RSA, and spot attacks such as birthday, replay, and chosen-plaintext. Expect scenario questions that reward judgment about which tool fits the situation rather than rote recall.
Related terms: Encryption, Public Key Infrastructure