- Confidentiality prevents unauthorized disclosure of sensitive information.
- Integrity guarantees that data has not been altered or tampered with.
- Authentication confirms the identity of communication parties.
### Fundamentals of Information Security
Cryptography is the mathematical science of securing communication against adversaries. Every cryptographic system strives to satisfy one or more key security objectives:
1. **Confidentiality**: Ensuring data remains readable only to authorized parties.
2. **Integrity**: Detecting unauthorized alterations to transmitted or stored data.
3. **Authentication**: Verifying the origin and true identity of entities or messages.
4. **Non-repudiation**: Preventing a sender from denying their prior action or signature.
#### Plaintext vs. Ciphertext
* **Plaintext ($M$)**: The original readable message or data.
* **Ciphertext ($C$)**: The obfuscated output resulting from applying an encryption algorithm $E$ with key $K$: $C = E(K, M)$.
* **Decryption ($D$)**: Reverting ciphertext back to plaintext using key $K$: $M = D(K, C)$.