Hello, I have noticed strange behavior in EvalRot. So I have a plaintext with the following elements (6 14 24 36 ...). If I encrypt, rotate by two, and then decrypt, I get the following plaintext (24 36 ...) but I need to have (24 36 6 14...). The rotation is in conjunction with addiction as foll…

Hi, Rotation is the full ciphertext which is ringsize/2 for CKKS and ringsize for BGV\BFV. the values that are not explicitly added when encrypting are zero. Are you trying to do a summation across the vector components? there is an EvalSum() for that I believe that uses binary tree addition over …

Please share your code in a minimal reproducible example Rotation So I have a plaintext with the following elements (6 14 24 36 ...). If I encrypt, rotate by two, and then decrypt, I get the following plaintext (24 36 ...) but I need to have (24 36 6 14...). This is expected behavior (not sure i…

[image] dcousins: Are you trying to do a summation across the vector components? There is an EvalSum() for that, I believe that uses binary tree addition over a power of two batch size (the non zero elements in the ciphertext). Yes, I am. I didn’t know that existed. Thanks a lot. I’m going t…

“Why does it put zeros at the end instead of the rotated elements?” When you encrypt a vector into a ciphertext, it actually stores it in the first available ‘slots’. There are ringsize/2 CKKS slots and ringsize BGV/BFV slots (there is a method that lets you get this value. ALL other locations are…

[image] dcousins: ct =[a b c 0 0 0 0] Rotated left one → [b c 0 0 0 0 a] rotated right one → [ 0 a b c 0 0 0] That was what I would expect. But if I rotate and then print the plaintext, I would get ct = [a b c 0 0 0 0] Rotate left one [b c 0 0 0 0 0]. I’m using BFV scheme with the predefined …

That’s because these plaintexts are often gigantic (1 << 17 elements long). So, if you print your values and limit it to the first N elements (size determined by your initial vector), you won’t see it.

Ah okay makes a lot of sense. Is there any way to change the Cyclotomic Order in the CCParams? I can only find in the documentation a function to display but not a “SetCyclotomicOrder”.

ringsize = cyclotomic order / 2 is a result of the security settings.

Hmm okay okay. Which security setting defines that?

[image] dcousins: “Why does it put zeros at the end instead of the rotated elements?” When you encrypt a vector into a ciphertext, it actually stores it in the first available ‘slots’. There are ringsize/2 CKKS slots and ringsize BGV/BFV slots (there is a method that lets you get this value. A…

EvalRot behaviour

Library Questions

ypolyakov March 18, 2023, 1:08am 12

The latter question has already been answered in Rotation in BFV

Topic		Replies	Views
Homomorphic Rotations between first and second half of the vector Library Questions	6	362	March 21, 2024
Incorrect result with rotation in BFV Library Questions	3	101	May 21, 2025
Rotation in BFV Library Questions	3	894	March 18, 2023
The result of rotation example for BFVrns Library Questions	1	297	October 27, 2022
Generating all possible rotations of a vector encrypted in a CKKS ciphertext FHE Questions	4	495	November 9, 2023

EvalRot behaviour

Related topics