eval_scheme_switching_setup: Comparison, minimum and maximum through scheme switching

In openfhe.R: R Interface to the 'OpenFHE' Fully Homomorphic Encryption Library

Comparison, minimum and maximum through scheme switching

Description

With switching set up in both directions, a comparison is done by switching CKKS values to FHEW, evaluating the sign there, and switching the result back (CKKS with real data and Feature$SCHEMESWITCH).

Usage

eval_scheme_switching_setup(cc, schswchparams)

eval_scheme_switching_key_gen(cc, key_pair, lwesk)

eval_compare_switch_precompute(cc, p_lwe = 0L, scale_sign = 1, unit = FALSE)

eval_compare_scheme_switching(
  ct1,
  ct2,
  num_ctxts = 0L,
  num_slots = 0L,
  p_lwe = 0L,
  scale_sign = 1,
  unit = FALSE
)

eval_min_scheme_switching(
  ct,
  public_key,
  num_values = 0L,
  num_slots = 0L,
  p_lwe = 0L,
  scale_sign = 1
)

eval_min_scheme_switching_alt(
  ct,
  public_key,
  num_values = 0L,
  num_slots = 0L,
  p_lwe = 0L,
  scale_sign = 1
)

eval_max_scheme_switching(
  ct,
  public_key,
  num_values = 0L,
  num_slots = 0L,
  p_lwe = 0L,
  scale_sign = 1
)

eval_max_scheme_switching_alt(
  ct,
  public_key,
  num_values = 0L,
  num_slots = 0L,
  p_lwe = 0L,
  scale_sign = 1
)

Arguments

cc	A CKKS CryptoContext.
schswchparams	A SchSwchParams object. The setup fills its CKKS fields from cc.
key_pair	The KeyPair of the CKKS context.
lwesk	The LWEPrivateKey of the FHEW context.
p_lwe	Integer; the FHEW plaintext modulus, 0L (default) for the library's choice.
scale_sign	Numeric; the scale applied before the sign is taken. Default 1.
unit	Logical; whether the input messages are normalized to the unit circle. Default FALSE.
ct1, ct2, ct	Ciphertext objects.
num_ctxts	Integer; number of values to compare, 0L (default) for all.
num_slots	Integer; number of CKKS slots, 0L (default) for the library's choice.
public_key	The PublicKey of the CKKS context.
num_values	Integer; number of values to take the minimum or maximum of, 0L (default) for all.

Details

eval_scheme_switching_setup() creates the FHEW context inside cc and returns its secret key; eval_scheme_switching_key_gen() generates the keys for both directions. eval_compare_switch_precompute() fixes the FHEW plaintext modulus and the scale of the comparison.

eval_compare_scheme_switching() returns a ciphertext whose slots hold 1 where ct1 < ct2 and 0 elsewhere. eval_min_scheme_switching() and eval_max_scheme_switching() return the minimum or maximum of the first num_values slots (a power of two) and its index; set up the context with set_compute_argmin(params, TRUE) for them. The index is one-hot encoded over num_values slots unless the parameters say otherwise (set_one_hot_encoding()). The slots after the first of the value, and after the index, hold no meaningful data. The ⁠_alt⁠ forms use more FHEW operations, for higher precision at a higher cost (set_use_alt_argmin(params, TRUE)).

Value

eval_scheme_switching_setup(): an LWEPrivateKey. eval_compare_scheme_switching(): a Ciphertext. The minimum and maximum functions: a list of two Ciphertext objects, the value and its index. The others: cc, invisibly.

See Also

eval_ckks_to_fhew(), eval_fhew_to_ckks()

openfhe.R documentation built on Nov. 13, 2026, 5:07 p.m.