BFV Parameters — BFVParams • openfhe

Constructor for the BFV scheme's CCParams surface. Every argument maps 1:1 to an upstream CCParams<CryptoContextBFVRNS>::Set* method whose override is not disabled in the BFV specialization. The 13 setters that BFV explicitly disables (SetScalingTechnique, SetFirstModSize, SetPRENumHops, SetExecutionMode, …) are not exposed here; see discovery D013.

Usage

BFVParams(
  plaintext_modulus = NULL,
  multiplicative_depth = NULL,
  scaling_mod_size = NULL,
  batch_size = NULL,
  security_level = NULL,
  secret_key_dist = NULL,
  key_switch_technique = NULL,
  ring_dim = NULL,
  digit_size = NULL,
  num_large_digits = NULL,
  standard_deviation = NULL,
  multiparty_mode = NULL,
  threshold_num_of_parties = NULL,
  multiplication_technique = NULL,
  max_relin_sk_deg = NULL,
  pre_mode = NULL,
  eval_add_count = NULL,
  key_switch_count = NULL,
  encryption_technique = NULL
)

Arguments

plaintext_modulus: Integer modulus t for the BFV plaintext space. BFV plaintexts are elements of Z_t[x]/Phi_m(x) and every homomorphic operation is performed modulo t. Must be a prime (or a composite supporting NTT in the batching case) and must be at least large enough that the end-to-end computation does not wrap modulo t. Typical values: 65537 (the smallest batching-friendly prime) for small-integer arithmetic, 786433 or larger when the operands or intermediate sums are larger. There is no scheme-level default — the user must supply one.
multiplicative_depth: Integer depth of the multiplication circuit the context must support. BFV and BGV grow ciphertext noise with each multiplication, and the ring modulus q is sized by OpenFHE to survive exactly multiplicative_depth successive multiplications plus an EvalAdd chain between them. Set to the exact depth of your circuit; setting it too small causes correctness failure at decrypt, setting it too large inflates ring dimension and slows every operation. Couples tightly to security_level (together they pin ring_dim).
scaling_mod_size: Integer bit-size of each intermediate scaling modulus in the RNS decomposition of q. Default leaves OpenFHE to choose from its internal tables (typically 60 bits). Override only when you know your depth budget needs a tighter value; the upstream simple-integers example uses the default.
batch_size: Integer number of SIMD-batched plaintext slots. Default is ring_dim / 2 under the full-packing convention. Set to a smaller power of two when your input vector is short and rotation cost dominates the circuit (the inner-product idiom). Must divide ring_dim / 2. Couples to ring_dim.
security_level: One of SecurityLevel$HEStd_128_classic (default when unset), HEStd_192_classic, HEStd_256_classic, and their _quantum counterparts. Fixes the target hardness assumption and, together with multiplicative_depth, determines the minimum ring dimension via the upstream lattice-parameters tables in core/lattice/stdlatticeparms.h.
secret_key_dist: One of SecretKeyDist$GAUSSIAN, UNIFORM_TERNARY (default under classic lattice parameters), or SPARSE_TERNARY. Controls the coefficient distribution of the secret key. Change only for research scenarios that demand a specific distribution; every production vignette uses the default.
key_switch_technique: One of KeySwitchTechnique$BV (default for BFV) or HYBRID. BV produces smaller evaluation keys and is the simpler option; HYBRID is relevant only when you are also setting num_large_digits and benchmarking rotation cost.
ring_dim: Integer power-of-two lattice ring dimension. Default (NULL) asks OpenFHE to compute the minimum ring dimension that satisfies security_level at the chosen multiplicative_depth. Override only to force a larger value than the auto-selection, typically to reserve headroom for later parameter sweeps.
digit_size: Integer r for BV key-switching: the base-2^r digit decomposition of the ciphertext during a key-switch. Default 0L selects the upstream default. Larger values decrease the number of digit multiplications at the cost of larger per-digit noise.
num_large_digits: Integer number of digit groupings in HYBRID key switching. Only meaningful when key_switch_technique = KeySwitchTechnique$HYBRID; ignored otherwise. Default 0L lets OpenFHE pick.
standard_deviation: Numeric standard deviation of the Gaussian error distribution used during key generation and encryption. Default (NULL) uses the upstream default 3.19. Override only in research scenarios.
multiparty_mode: One of MultipartyMode$FIXED_NOISE_MULTIPARTY or NOISE_FLOODING_MULTIPARTY. Selects between threshold-FHE with fixed noise (no flooding) and noise-flooding-protected threshold-FHE. Both cox-threshold and CVXR-consensus-ADMM vignettes rely on threshold paths; leave at upstream default unless you are intentionally tuning the leakage/performance trade-off.
threshold_num_of_parties: Integer count of parties in an n-of-n threshold protocol. Ignored in non-threshold contexts. The cox-threshold vignette uses 2; the threshold-fhe-5p Python example uses 5.
multiplication_technique: One of MultiplicationTechnique$BEHZ, HPS, HPSPOVERQ, HPSPOVERQLEVELED. BFV-specific choice of how the plaintext modulus interacts with the ciphertext modulus during multiply. Default upstream is HPSPOVERQLEVELED; override only if you are benchmarking multiplication-path variants.
max_relin_sk_deg: parity-deferred: maximum degree of the secret key that can be relinearized. Upstream default is 2. No current vignette or Python example exercises this; the cpp11 binding is in place so a later release can promote it without a recompile.
pre_mode: parity-deferred: proxy re-encryption mode (PREMode$NOT_SET, INDCPA, FIXED_NOISE_HRA, NOISE_FLOODING_HRA). Only meaningful if the PRE feature is enabled on the context. No current vignette uses PRE.
eval_add_count: parity-deferred: upstream noise-budget hint: maximum additions between multiplications. Used only by the noise-flooding path. Default 0.
key_switch_count: parity-deferred: upstream noise-budget hint: maximum key-switch count. Default 0.
encryption_technique: parity-deferred: BFV-specific encryption variant (EncryptionTechnique$STANDARD or EXTENDED). Default STANDARD.

Value

A BFVParams S7 object.