up:: [[Post-Quantum Cryptography (PQC)]] # Key Encapsulation Key Encapsulation is a method used in [[cryptography]] to securely transfer [[encryption]] keys between parties. It involves encapsulating a secret key within an encrypted message, using the recipient's [[public key]], so that only the recipient can decrypt the message to extract the secret key. ## How It Works 1. **Key Generation:** The sender generates a temporary, random [[encryption]] key intended for encrypting the actual data (plaintext). 2. **Encapsulation:** This key is then encapsulated (encrypted) using the recipient's [[public key]]. 3. **Transmission:** The encapsulated key, along with the encrypted data, is sent to the recipient. 4. **Decapsulation:** Upon receiving, the recipient uses their [[private key]] to decapsulate (decrypt) the encapsulated key. 5. **Usage:** The recipient then uses the decrypted key to decrypt the data (ciphertext). ## Advantages - **Security:** Since the key is encrypted, it is secure from interception during transmission. - **Efficiency:** Reduces the complexity and size of data [[encryption]] by allowing bulk data to be encrypted with a symmetric key, which is then securely transmitted via key encapsulation. - **Flexibility:** Can be integrated with various [[encryption]] schemes and supports hybrid approaches combining the efficiency of [[Symmetric Cryptography|symmetric encryption]] with the security of [[asymmetric encryption]]. ## Major Tools - **Libsodium:** Provides a platform for implementing modern, easy-to-use software libraries for [[encryption]], decryption, signatures, password hashing, and more. - **RSA BSAFE:** A suite of [[FIPS 140-2]] validated cryptographic libraries that support key encapsulation among other cryptographic functions. - **OpenSSL:** A robust, commercial-grade, full-featured toolkit for general-purpose [[cryptography]] and secure communication, supports key encapsulation mechanisms. ## Related Cybersecurity Policies - **[[NIST Special Publication 800-56B]],** "Recommendation for Pair-Wise Key-Establishment Schemes Using Integer Factorization Cryptography": Includes guidance on using [[RSA]] for key encapsulation. - **[[NIST Special Publication 800-56C]],** "Recommendation for Key-Derivation Methods in Key-Establishment Schemes": Provides recommendations on combining symmetric and asymmetric key establishment techniques for enhanced security. - **[[ISOIEC 19772]],** "Information technology - Security techniques - Authenticated [[encryption]]": Covers standards for [[encryption]] and key management, including key encapsulation. ## Best Practices - Ensure that the public/[[private key]] pairs used for encapsulation/decapsulation are managed securely and replaced periodically. - Use proven cryptographic libraries and tools that adhere to current standards and have been audited for security vulnerabilities. - Combine key encapsulation with robust end-to-end [[encryption]] methods to secure both the transmission of the key and the data. ## Current Status Key encapsulation remains a critical component of secure cryptographic implementations, especially important in scenarios involving secure key exchange over untrusted networks. Advances in [[quantum computing]] have started prompting research into [[quantum-resistant]] key encapsulation methods. ## Revision History - **2024-04-14:** Entry created.