feat: add Encryption Algorithms and Security Considerations article

Author: xrissoula

docs/reference/encryption-algorithms.md

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+---
+title: 'Encryption Algorithms and Security Considerations'
+date: 2025-03-12
+author: 'Christina'
+tags: ['cryptography', 'security', 'encryption', 'key-management', 'polykey']
+---
+
+# Encryption Algorithms and Security Considerations
+
+## Overview
+
+Polykey's security model is built on modern cryptographic principles to ensure confidentiality, integrity, and authentication across all operations. This document outlines the encryption algorithms Polykey employs, their strengths, and key security considerations for maintaining a secure system.
+
+## Encryption Algorithms Used in Polykey
+
+Polykey integrates a hybrid cryptosystem, combining symmetric and asymmetric cryptographic algorithms for optimal security and performance.
+
+### Symmetric Encryption
+* **AES-GCM (Advanced Encryption Standard - Galois/Counter Mode)**
+   * Used for encrypting data at rest and in transit.
+   * Provides both encryption and authentication in a single step.
+   * 256-bit key length for strong security.
+   * Resistant to padding oracle attacks due to its authenticated encryption structure.
+
+### Asymmetric Encryption
+* **X25519 (Elliptic Curve Diffie-Hellman)**
+   * Used for key exchange and secure session establishment.
+   * Based on Curve25519, which is efficient and resistant to side*channel attacks.
+   * Provides forward secrecy by generating ephemeral session keys.
+
+* **Ed25519 (Elliptic Curve Digital Signature Algorithm)**
+   * Used for signing and verifying messages and transactions.
+   * Strong resistance to side-channel attacks.
+   * Deterministic signatures prevent nonce-related vulnerabilities.
+
+### Key Encapsulation Mechanism (KEM)
+* **ECIES (Elliptic Curve Integrated Encryption Scheme)**
+   * Facilitates secure encryption of symmetric keys during key exchange.
+   * Uses elliptic curve cryptography for efficient and secure key wrapping.
+   * Ensures confidentiality and authenticity of the exchanged key.
+
+## Security Considerations
+
+### 1. Key Management
+* **Recovery Codes:** Users must securely store their 24-word recovery code, as Polykey does not store private keys.
+* **Key Rotation:** Regular key rotation mitigates the risk of long-term key exposure.
+* **Secure Storage:** Encrypted key material must be stored in a secure environment to prevent unauthorized access.
+
+### 2. Forward Secrecy
+* Polykey ensures forward secrecy through ephemeral key exchange using X25519.
+* If a private key is compromised, past communications remain secure.
+
+### 3. Authentication & Integrity
+* Digital signatures (Ed25519) ensure data authenticity and prevent tampering.
+* Authenticated encryption (AES-GCM) guarantees data integrity.
+
+### 4. Resistance to Quantum Threats
+* While current encryption methods are secure, future quantum computing advancements may break classical cryptography.
+* Polykey's roadmap includes exploring post-quantum cryptographic alternatives.
+
+### 5. Attack Surface Reduction
+* Minimizing reliance on outdated cryptographic algorithms.
+* Eliminating common cryptographic pitfalls such as RSA-based key exchanges, which are vulnerable to decryption with modern computing power.
+
+## Conclusion
+
+Polykey employs a combination of AES-GCM, X25519, Ed25519, and ECIES to ensure strong security across all cryptographic operations. By following best practices in key management, forward secrecy, and attack surface reduction, Polykey maintains a robust security posture. Future updates may incorporate post-quantum cryptographic schemes to address emerging threats.