E2E near-standard hybrid encryption

Background: homomorphic encryption (HE) ciphertexts possess larger communication and storage costs compared to symmetrically encrypted ciphertexts. Hybrid encryption (Transciphering) allows to encrypt data using symmetric ciphertexts and decrypt it under FHE. However, the decryption process is either considered slow or did not use standardized symmetric schemes, which prevented users from using Hybrid encryption in the real world. Another barrier is that today, it is recommended to use an AEAD scheme instead of just symmetric encryption to protect the integrity of the data.

Our contribution:

• We provide the first practical implementation of hybrid encryption using AES-CTR, implemented using HELayers and HEaaN.
• We also provide the first AEAD hybrid encryption that uses AES-GCM.
• Our solution works for integers and floating-point elements and take into consideration SIMD packing such as tile tensors.