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Important note: These tools are for learning/demos. Do not paste real passwords, private keys you actually use, or sensitive personal/company data.

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Introduction

Cryptography is the practice of protecting information using mathematics. In modern computing, cryptography is mainly used to achieve:
  1. Confidentiality — keep data secret from unauthorized parties
  2. Integrity — detect if data has been modified
  3. Authenticity — prove who created/sent the data
  4. Non-repudiation — the sender cannot reasonably deny signing/approving something
Two major families of encryption exist: A) Symmetric cryptography (AES)
  • One shared secret key encrypts and decrypts
  • Very fast and efficient
  • Main challenge: securely sharing that secret key
B) Asymmetric cryptography (RSA)
  • Uses a public key + private key pair
  • Public key can be shared openly; private key stays secret
  • Solves key sharing and enables digital signatures
  • Slower and heavier than symmetric encryption
If you remember one idea: AES is built to encrypt lots of data quickly, while RSA is built to securely exchange keys and prove identity (signatures). In practice, they are usually used together.