🔐 Cryptography Basics
Cryptography is the art and science of securing data. It includes techniques for hiding data (encryption), verifying data (hashing), and proving identities (digital signatures).
🔁 Hashing Algorithms
- SHA-256: Secure Hash Algorithm used to verify data integrity.
- MD5: Produces 128-bit digest, vulnerable to collisions.
- Birthday attack: Exploits hash collisions for forgery.
🔑 Symmetric & Asymmetric Encryption
Symmetric encryption uses the same key to encrypt and decrypt (e.g., AES, DES). It is fast and good for bulk data.
Asymmetric encryption uses a key pair: public and private keys. It is used for authentication, digital signatures, and key exchange (e.g., RSA).
⚙️ Cipher Modes & Suites
Cipher suites combine key exchange, encryption, and hashing algorithms. Common cipher modes include ECB, CBC, and GCM. Asymmetric systems like PKI support authentication and integrity.
📦 Certificates & PKI
- PKI: Uses Certificate Authorities (CAs) to issue digital certificates and bind public keys to identities.
- Digital Certificate: Contains subject info, public key, issuer, validity period, etc. Learn more on Wikipedia.
- CSR: Certificate Signing Request submitted to a CA. Learn more from DigiCert.
- Certificate Lifecycle: Includes generation, renewal, suspension, and revocation. Learn more from SSL.com.
🧠 Cryptographic Use Cases
- Confidentiality: Encrypting sensitive files or communications. Learn more about encryption on Wikipedia.
- Integrity: Verifying files with checksums or hashes. Learn more about hashing on Wikipedia.
- Authentication: Digital certificates prove identity. Learn more about authentication on Wikipedia.
- Non-repudiation: Digital signatures prevent denial of authorship. Learn more about digital signatures on Wikipedia.
🔒 Advanced Techniques
- Salting: Random data added to passwords before hashing to resist attacks. Learn more about salting on Wikipedia.
- Key stretching: PBKDF2 increases complexity of brute-force attacks. Learn more about PBKDF2 on Wikipedia.
- Homomorphic encryption: Enables computation on encrypted data. Learn more about homomorphic encryption on Wikipedia.
- Steganography: Hides information within other media (e.g., images). Learn more about steganography on Wikipedia.
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