rotate

Fixed Rotation Key-Based Rotation

Engine.rotate(ciphertext, fixed_rotation_key)
Rotates the input ciphertext to the right by the delta value specified in the fixed rotation key. For example, rotating [1, 2, 3, 4] by 1 results in [4, 1, 2, 3]. In general, does not consume any level. A level is consumed only if the operation is not a multiparty computation and the ciphertext is at the maximum allowable level for a given parameter.
  • Input:
    • Ciphertext
    • FixedRotationKey
  • Output:
    • Ciphertext
from desilofhe import Engine

engine = Engine()
secret_key = engine.create_secret_key()
public_key = engine.create_public_key(secret_key)
fixed_rotation_key = engine.create_fixed_rotation_key(secret_key, delta=1)

message = [1, 2, 3]
ciphertext = engine.encrypt(message, public_key)
rotated_ciphertext = engine.rotate(ciphertext, fixed_rotation_key)

Fixed rotation keys allow rotation by a specific delta value only. If you need various rotations, using multiple rotations with fixed rotation key of delta 1 is less efficient than employing general rotation keys. However, if a specific rotation is frequently performed, generating a fixed rotation key for that value is more optimal.

Rotation Key-Based Rotation

Engine.rotate(ciphertext, rotation_key, delta)
Rotates the input ciphertext to the right by the specified delta value. For example, rotating [1, 2, 3, 4] by 1 results in [4, 1, 2, 3]. In general, does not consume any level. A level is consumed only if the operation is not a multiparty computation and the ciphertext is at the maximum allowable level for a given parameter.
  • Input:
    • Ciphertext
    • RotationKey
    • delta: int
  • Output:
    • Ciphertext
from desilofhe import Engine

engine = Engine()
secret_key = engine.create_secret_key()
public_key = engine.create_public_key(secret_key)
rotation_key = engine.create_rotation_key(secret_key)

message = [1, 2, 3]
ciphertext = engine.encrypt(message, public_key)
rotated_ciphertext = engine.rotate(ciphertext, rotation_key, delta=1)

Rotation keys are constructed using a set of \(2^n\) rotations. When the delta is not a power of 2, the rotation is achieved internally through multiple rotations. If many different rotations are needed, general rotation keys are more efficient. For frequent rotations by specific values, generating a fixed rotation key for that value is more optimal.

Plaintext Rotation

Engine.rotate(plaintext, delta)
Rotates the input plaintext to the right by the specified delta value. For example, rotating [1, 2, 3, 4] by 1 results in [4, 1, 2, 3].
  • Input:
    • Plaintext
    • delta: int
  • Output:
    • Plaintext
from desilofhe import Engine

engine = Engine()

message = [1, 2, 3]
plaintext = engine.encode(message)
rotated_plaintext = engine.rotate(plaintext, delta=1)