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Sections
Learn
Foundations
- The history and purpose of cryptographyQuiz · Slides
- The math underneath: modular arithmetic & one-way functionsQuiz · Slides
- Hash functions & digital signaturesQuiz · Slides
- Password hashing & key derivation: PBKDF2, bcrypt, scrypt, Argon2Quiz · Slides
- Key sizes & security levels: what the numbers meanQuiz · Slides
- Random number generation: the primitive everything else depends onQuiz · Slides
- Entropy: measuring, estimating, and testing true randomnessQuiz · Slides
- Why quantum computers break this: Shor's algorithmQuiz · Slides
Symmetric-key
Public-key
Protocols
- Diffie-Hellman key exchangeQuiz · Slides
- X.509 certificates & the PKI trust hierarchyQuiz · Slides
- JSON Web Tokens & API authenticationQuiz · Slides
- Passkeys & WebAuthnQuiz · Slides
- SSH: key exchange, host keys, and authenticationQuiz · Slides
- TLS in practice: how HTTPS puts it all togetherQuiz · Slides
- End-to-end encrypted messaging: the Signal ProtocolQuiz · Slides
Use Cases
Key Management
PKI & Certificates
Identity & Access
Payments
- Key ceremonies and the HSM key hierarchy: where every payment key comes fromQuiz · Slides
- PIN blocks: encrypting a 4-digit number like it's a nuclear launch codeQuiz · Slides
- CVV/CVC: the three digits that never survive an authorizationQuiz · Slides
- EMV chip authentication: the conversation behind every chip transactionQuiz · Slides
- 3-D Secure and tokenization: protecting a transaction that never touches a chipQuiz · Slides
- DUKPT: a fresh key for every card payment at the counterQuiz · Slides
Standards
Standards bodies
- NIST: the standards body behind AES, SHA, and post-quantum cryptographyQuiz · Slides
- The IETF: RFCs and the protocols the internet actually runsQuiz · Slides
- ISO/IEC: the paywalled standards behind ISMS certification and algorithm testingQuiz · Slides
- OASIS: where the identity and PKI-token standards actually get writtenQuiz · Slides
- EMVCo & PCI SSC: the industry bodies behind chip cards, CVVs, and complianceQuiz · Slides
Certification programs
Playground
Symmetric-key
Foundations
Public-key
- RSA key generation & OAEP encryptionHow it works
- RSA-PSS sign & verifyHow it works
- ECDSA sign & verifyHow it works
- Ed25519 sign & verifyHow it works
- ECDH key exchangeHow it works
- Envelope encryption & key wrappingHow it works
- Certificate chain builderHow it works
- Certificate revocation: valid signature, still not trustedHow it works
- A PKCS#11 session, using real keysHow it works
Protocols
Payments
- PIN block builder & translatorHow it works
- CVV/CVC calculatorHow it works
- EMV ARQC/ARPC simulatorHow it works
- 3DS message flow & JWS signingHow it works
- Illustrative CAVV generatorHow it works
- Network tokenizationHow it works
- TR-31 / X9.143 key block builder & parserHow it works
- DUKPT key derivation: TDES (X9.24-1) and AES (X9.24-3)How it works