Revisiting the Slot-to-Coefficient Transformation for BGV and BFV

ePrint Report: Revisiting the Slot-to-Coefficient Transformation for BGV and BFV

Robin Geelen

Numerous algorithms in homomorphic encryption require an operation that moves the slots of a ciphertext to the coefficients of a different ciphertext. We describe an FFT-like method for decomposing this slot-to-coefficient transformation (and its inverse) for BGV and BFV. The proposed method is specific to power-of-two cyclotomic rings and can handle both fully and sparsely packed slots. Previously, such a method was only known for non-power-of-two cyclotomic rings. …

algorithms bfv ciphertext encryption eprint report homomorphic encryption report robin transformation