12 key functions commonly offered in cryptographic services:

1. Encryption and Decryption

• Purpose: Protect data confidentiality by converting plain text into an unreadable format (encryption) and restoring it to its original form (decryption) when needed.

• Types:

  • Symmetric Encryption: Uses a single key for both encryption and decryption (e.g., AES).

  • Asymmetric Encryption: Uses a pair of keys – public key for encryption and private key for decryption (e.g., RSA).

2. Hashing

• Purpose: Create a fixed-size, unique representation (hash) of data to verify its integrity.

• Key Features:

  • One-way function (irreversible).

  • Common algorithms: SHA-256, MD5.

• Use Cases:

  • Password storage.

  • Data integrity verification.

3. Digital Signatures

• Purpose: Verify the authenticity and integrity of a message or document.

• How It Works:

  • Sender encrypts a hash of the message using their private key.

  • Receiver uses the sender's public key to validate the signature.

• Use Cases:

  • Signing emails, contracts, and software.

4. Key Management

• Purpose: Handle the generation, distribution, storage, and rotation of cryptographic keys securely.

• Key Components:

  • Key generation: Create strong, random keys.

  • Key storage: Secure repositories for key protection.

  • Key exchange: Safely share keys between parties (e.g., Diffie-Hellman).

5. Authentication

• Purpose: Verify the identity of users, devices, or systems.

• Methods:

  • Password-based authentication.

  • Public Key Infrastructure (PKI): Certificate-based authentication using digital certificates.

6. Integrity Verification

• Purpose: Ensure data hasn’t been tampered with during transmission or storage.

• Techniques:

  • Message Authentication Codes (MACs): Use a secret key for verification.

  • Hash-based MACs (HMAC): Combine hashing with a secret key.

7. Secure Communication

• Purpose: Enable encrypted communication between parties.

• Examples:

  • Transport Layer Security (TLS): Secure web communication.

  • Secure Shell (SSH): Encrypted remote server access.

8. Non-repudiation

• Purpose: Ensure a sender cannot deny their actions (e.g., sending a message).

• Implementation: Use digital signatures to provide proof of origin.

9. Random Number Generation

• Purpose: Generate random numbers for cryptographic operations (e.g., key generation).

• Types:

  • Pseudo-random Number Generators (PRNGs).

  • True Random Number Generators (TRNGs).

10. Certificate Management

• Purpose: Manage digital certificates for secure communications.

• Key Elements:

  • Certificate issuance, renewal, and revocation.

  • Certificate Authorities (CAs) for trust management.

11. Access Control

• Purpose: Restrict access to resources using cryptographic techniques.

• Examples:

  • Role-Based Access Control (RBAC).

  • Attribute-Based Encryption (ABE).

12. Post-Quantum Cryptography (Emerging Field)

• Purpose: Develop algorithms resistant to attacks by quantum computers.

• Focus Areas:

  • Lattice-based cryptography.

  • Code-based cryptography.

Cryptography functions are often combined to build secure systems, such as virtual private networks (VPNs), blockchain, and secure messaging platforms.