Crate poulpy_ckks 

poulpy-ckks

Backend-agnostic implementation of the CKKS (Cheon-Kim-Kim-Song) homomorphic encryption scheme, built on top of the low-level primitives provided by poulpy-core, poulpy-hal, and the available compute backends (poulpy-cpu-ref, poulpy-cpu-avx).

The crate uses a bivariate polynomial representation over the Torus (base-2^{base2k} digits) instead of the RNS representation used by most other CKKS libraries. Public precision management is exposed through CKKSMeta:

• log_delta: base-2 logarithm of the encoded plaintext scaling factor
• log_budget: remaining homomorphic headroom, also tracked in bits

CKKSMeta also records the SlotsKind of a value: whether its slots are known to be real, or may carry an imaginary part. Operations compose that claim, keeping Real only when every operand is real, so a caller can state it once at encoding time and have the pipelines specialize on it.

Together they define the semantic torus width of a value: k() = log_delta + log_budget. Storage is rounded up to the next multiple of base2k, so the allocated capacity max_k() may exceed the effective width k(). Arithmetic APIs update this metadata for you; buffers always stay at their allocated width, and allocating a destination at exactly the k you want is how results are narrowed.

Safe add/sub operations return K-normalized ciphertexts. Their unnormalized variants live on api::CKKSAddOps and api::CKKSSubOps and write into an layouts::UnnormalizedCKKSCiphertext for callers who want to fuse several linear steps before normalizing explicitly. Limb digits in that wrapper may hold un-propagated carries (wider than base2k bits), so passing it to any DFT-domain primitive (keyswitching, convolution, automorphisms) would produce incorrect decryptions. The wrapper does not implement GLWEToBackendRef or GLWEToBackendMut, making such misuse a compile error. Call layouts::UnnormalizedCKKSCiphertext::normalize before the next keyswitching or convolution step.

Modules

Module	Role
approximation	Reusable minimax fitting, precision/depth selection, composite sign generation, and prepared interval-mapped polynomial evaluation
encoding	CKKS encoders/decoders, including slot-wise real/imaginary packing
layouts	CKKS ciphertext/plaintext wrappers and metadata-aware allocation helpers
presets	Ready-to-use parameter sets
api	The public op traits: leveled arithmetic (add, sub, mul, neg, rotate, conjugate), encryption, decryption, rescale, and scratch sizing
api::CKKSBootstrappingOps	The CKKS bootstrapping pipeline: its one native primitive ModUp (modulus raise), plus CoeffsToSlots / SlotsToCoeffs and EvalMod re-exported as supertraits (api::CKKSDFTOps / api::CKKSEvalModOps); parameterized by layouts::BootstrappingPlan
api::CKKSPaCoOps	PaCo bootstrapping without ModUp or EvalMod; parameterized by layouts::PaCoPlan and a compiled layouts::PaCoContext

Re-exports

pub use scalar::Quad;

Modules

api

approximation

Reusable host-side polynomial approximation planning.

default

encoding

Backend-independent CKKS encoding algorithms.

layouts

CKKS-level data structures.

oep

Backend override seams: one unsafe trait CKKS*Impl<BE> per op family.

polynomial

power_basis

prelude

One-stop imports for the common CKKS path.

presets

Ready-to-use CKKS parameter sets.

scalar

Portable quad-precision (IEEE 754 binary128) scalar for high-precision CKKS.

Macros

impl_ckks_add_defaults

impl_ckks_conjugate_defaults

impl_ckks_copy_defaults

impl_ckks_dft_defaults

Wires a backend into the reference homomorphic-DFT chain: implements the [DFTDefault] and [DFTMatrixDefault] marker impls, inheriting every default-bodied method (which forward to crate::default::dft).

impl_ckks_encapsulated_mod_up_default

Opts a backend into the CKKS reference encapsulated-ModUp pipeline.

impl_ckks_encryption_defaults

impl_ckks_imag_defaults

impl_ckks_infos

Implements the full CKKS scratch-view trait bundle for a nominal backend view wrapper: CKKSInfos, SetCKKSInfos, SetK, BSGSMeta, and SetBSGSMeta.

impl_ckks_mul_defaults

impl_ckks_neg_defaults

impl_ckks_plaintext_defaults

impl_ckks_pow2_defaults

impl_ckks_rotate_defaults

impl_ckks_sub_defaults

Structs

CKKSLayout

Allocation / precision spec for a CKKS value.

CKKSMeta

CKKS semantic precision metadata carried by ciphertexts and plaintexts.

CoeffsMeta

Coefficient metadata for plan-compiled operands: the DFT factor diagonals (layouts::DFTPlan), the EvalMod polynomial coefficients (layouts::EvalModPlan), and the BSGS polynomial encoders (polynomial::EncodeBSGS).

Enums

CKKSCompositionError

CKKS composition and alignment errors returned by high-level operations.

CKKSError

Typed error returned by every fallible CKKS operation (the api op traits and the layers backing them).

SlotsKind

Which subfield the encoded slots are known to live in.

Traits

CKKSCtBounds

Marker bound for CKKS ciphertext type parameters.

CKKSInfos

Common metadata accessors for CKKS ciphertext and plaintext containers.

CKKSPlaintextToBackendMut

Backend-compatible mutable CKKS plaintext storage.

CKKSPlaintextToBackendRef

Backend-compatible shared CKKS plaintext storage.

SetCKKSInfos

Mutable CKKS metadata access for ciphertext/plaintext containers.

Type Aliases

CKKSResult

Result type of every fallible CKKS operation.