Class StdLatticeParm

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Class Documentation

class lbcrypto::StdLatticeParm

One row of the Homomorphic Encryption Standard parameter tables: for a secret key distribution, a ring dimension, and a security level, the largest supported bit size of the ciphertext modulus. The rows are stored in a static table and indexed by (distribution, security level), then by ring dimension (FindMaxQ) or by modulus bit size (FindRingDim).

Public Functions

inline StdLatticeParm(DistributionType distType, uint32_t ringDim, SecurityLevel minSecLev, uint32_t maxLogQ)

Constructs one table row.

Parameters

  • distType – secret key distribution

  • ringDim – ring dimension

  • minSecLev – security level the row is certified for

  • maxLogQ – largest supported bit size of the ciphertext modulus

inline DistributionType getDistType() const
inline uint32_t getRingDim() const
inline SecurityLevel getMinSecLev() const
inline uint32_t getMaxLogQ() const

Public Static Functions

static inline void initializeLookups()

Builds the lookup maps (by ring dimension and by modulus bit size) from the static table of rows. Called on first use by FindMaxQ and FindRingDim.

static inline uint32_t FindMaxQ(DistributionType distType, SecurityLevel minSecLev, uint32_t ringDim)

Looks up the largest supported ciphertext modulus bit size for a ring dimension.

Parameters

  • distType – secret key distribution

  • minSecLev – required security level

  • ringDim – ring dimension

Returns

the maximum log2 of the ciphertext modulus, or 0 if the table has no row for this ring dimension

static inline uint32_t FindRingDim(DistributionType distType, SecurityLevel minSecLev, uint32_t curLogQ)

Finds the smallest tabulated ring dimension whose maximum modulus bit size is at least curLogQ.

Parameters

  • distType – secret key distribution

  • minSecLev – required security level

  • curLogQ – log2 of the ciphertext modulus

Returns

the ring dimension, or twice the largest tabulated ring dimension if curLogQ exceeds every table row