What is Cryptography?
Cryptography is the science of securing information through mathematical techniques. It transforms readable data (plaintext) into an unreadable format (ciphertext) and back, protecting data confidentiality, integrity, and authenticity.
Cryptographic Goals
Confidentiality Only authorized parties can read data.
Integrity Data hasn't been altered.
Authentication Verify identity of parties.
Non-repudiation Cannot deny actions.
Types of Cryptography
Symmetric Encryption
- Same key for encrypt/decrypt
- Fast, efficient
- Examples: AES, ChaCha20
Asymmetric Encryption
- Public/private key pairs
- Slower, key exchange solved
- Examples: RSA, ECC
Hash Functions
- One-way transformation
- Fixed output length
- Examples: SHA-256, SHA-3
Digital Signatures
- Verify authenticity
- Non-repudiation
- Examples: RSA, ECDSA
Common Algorithms
| Type | Algorithm | Use Case |
|---|---|---|
| Symmetric | AES-256 | Data encryption |
| Asymmetric | RSA-2048 | Key exchange |
| Hash | SHA-256 | Integrity |
| Signature | ECDSA | Authentication |
Modern Applications
- TLS/SSL (HTTPS)
- End-to-end encryption
- Digital signatures
- Password hashing
- Blockchain
- Secure messaging