Learning outcomes
- Distinguish hashes, MACs, signatures, authenticated encryption, key derivation, and random generation.
- Design key custody, envelope encryption, record formats, nonce rules, recovery, and rotation.
- Apply classification, minimization, retention, and secure deletion across every data copy.
- Inventory and migrate cryptography, including post-quantum changes, without downgrade or hidden dependencies.
Scenario
A multi-tenant service stores recovery credentials and signed audit artifacts for several years. It must protect database and backup compromise, isolate tenant key use, restore data, remove expired records, and migrate algorithms without losing availability or verification.
Ordered learning units
Data Classification
Assign data sensitivity, criticality, ownership, use, sharing, retention, and recovery requirements that drive technical controls.
Data Minimization and Purpose Limitation
Collect, use, expose, and retain only the data necessary for a stated operational purpose and bounded period.
Protect the data lifecycle
Control collection, use, sharing, storage, logging, backup, recovery, retention, deletion, and sanitization for one data class.
Cryptographic Hash Function
Map data to a fixed-length digest with defined preimage, second-preimage, and collision resistance for the selected use.
Message Authentication Code (MAC)
Verify message integrity and shared-key origin with a standard MAC while controlling key scope, context, replay, and verification.
Digital Signature
Bind a defined message to a private signing key and verify it through an authenticated public key, purpose, and context.
Cryptographic Randomness and Entropy
Generate unpredictable security values from a validated entropy source and cryptographic random-bit generator with protected state.
Key Derivation Function (KDF)
Derive purpose-separated cryptographic keys from suitable key material with a standard KDF, salt, context, and output length.
Authenticated Encryption with Associated Data (AEAD)
Encrypt plaintext and authenticate ciphertext plus unencrypted context with a standard AEAD construction and correct nonce handling.
Nonce and Initialization Vector
Apply the exact uniqueness, unpredictability, length, and state rules that a cryptographic construction requires for each key.
Cryptographic Key Management
Control cryptographic key purpose, generation, custody, distribution, use, rotation, compromise, recovery, and destruction.
Key Management Service and HSM
Separate key lifecycle orchestration, hardware protection, cryptographic operations, workload authorization, and application data policy.
Envelope Encryption
Encrypt data with a data-encryption key and protect that key under a separately stored key-encryption key or key service.
Design application cryptography
Select a standard construction and define keys, nonces, context, record format, failure behavior, tests, and migration before coding.
Protect application data with cryptography
Choose transport, application, database, filesystem, storage, and in-use protections from the data threat model and key boundary.
Data Retention and Secure Deletion
Retain data for a stated need, then remove access across primary storage, replicas, caches, backups, indexes, keys, and media.
Cryptographic Agility
Inventory and replace algorithms, parameters, protocols, keys, libraries, certificates, and stored formats without hidden dependencies.
Post-Quantum Cryptography
Prepare public-key systems for quantum-resistant key establishment and signatures through inventory, standards, testing, and migration.
Plan a cryptographic migration
Inventory cryptographic dependencies and migrate protocols, algorithms, keys, certificates, code, hardware, and stored data safely.
Evaluation questions
- Which security property and threat boundary does each cryptographic mechanism protect?
- Are key purpose, scope, custody, nonce, context, record format, authorization, and failure behavior explicit?
- Can every data copy be found, recovered, retained, deleted, and sanitized according to its classification?
- Can the system migrate and reject old cryptography without hidden consumers, downgrade, or loss of required data?
Completion conditions
- Produce a plaintext, ciphertext, key, identity, copy, and recovery map for one sensitive data class.
- Implement or review a versioned authenticated-encryption record and its negative tests without designing a new primitive.
- Run one key rotation, one isolated backup restore, one deletion verification, and one old-format rejection test.
