Compiler backend

The Concrete backends are implementations of the cryptographic primitives of the Zama variant of TFHE. The compiler emits code which combines call into these backends to perform more complex homomorphic operations.

There are client and server features.

Client features are:

• private (G)LWE key generation (currently random bits)

• encryption of ciphertexts using a private key

• public key generation from private keys for keyswitch, bootstrap or private packing

• (de)serialization of ciphertexts and public keys (also needed server side)

Server features are homomorphic operations on ciphertexts:

• linear operations (multisums with plain weights)

• keyswitch

• simple PBS

• WoP PBS

There are currently 2 backends:

• concrete-cpu which implements both client and server features targeting the CPU.

• concrete-cuda which implements only server features targeting GPUs to accelerate homomorphic circuit evaluation.

The compiler uses concrete-cpu for the client and can use either concrete-cpu or concrete-cuda for the server.