Fully Homomorphic Encryption EVM (fhEVM)

Cypher introduces the Fully Homomorphic Encryption Virtual Machine (fhEVM), a transformative execution layer that enables encrypted computations within smart contracts. This ensures both the logic and the data remain encrypted throughout their lifecycle, revolutionizing blockchain privacy. Key technical features include:

Encrypted Smart Contract Execution

• Supports arbitrary computations on encrypted data directly on-chain without exposing sensitive information.

• Execution logic is processed securely within the fhEVM using TFHE-based primitives (e.g., TFHE.add, TFHE.sub, TFHE.mul).

• Enables privacy-preserving decentralized applications by allowing fully encrypted workflows from input to output.

Encrypted Data Types

Provides native support for encrypted primitives, including:

• Encrypted integers (euint64, euint32, etc.).

• Encrypted booleans (ebool) for logical operations.

• Encrypted arrays for handling structured data.

• Operators like addition, subtraction, and comparison (TFHE.gt, TFHE.eq) are natively overloaded to handle encrypted types, eliminating the need for manual handling.

Secure Multiparty Operations

• Enables collaborative encrypted computations across distributed nodes, ensuring confidentiality of inputs and outputs.

• Supports complex workflows like federated machine learning and secure multiparty analytics.

• Access control is enforced through features like Access Control Lists (ACL), which define permissions on ciphertext manipulation.

Dynamic Key Management:

• Implements hierarchical, decentralized encryption key schemes for secure and seamless encryption workflows.

• Supports re-encryption for transitioning ciphertext ownership while preserving privacy and trust.

• Leverages NaCl public-private key pairs for client-side decryption post-re-encryption.