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evaluator.go
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/
evaluator.go
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package rgsw
import (
"github.com/tuneinsight/lattigo/v4/ring"
"github.com/tuneinsight/lattigo/v4/rlwe"
"github.com/tuneinsight/lattigo/v4/rlwe/ringqp"
)
// Evaluator is a type for evaluating homomorphic operations involving RGSW ciphertexts.
// It currently supports the external product between a RLWE and a RGSW ciphertext (see
// Evaluator.ExternalProduct).
type Evaluator struct {
rlwe.Evaluator
params rlwe.Parameters
}
// NewEvaluator creates a new Evaluator type supporting RGSW operations in addition
// to rlwe.Evaluator operations.
func NewEvaluator(params rlwe.Parameters, evk *rlwe.EvaluationKey) *Evaluator {
return &Evaluator{*rlwe.NewEvaluator(params, evk), params}
}
// ShallowCopy creates a shallow copy of this Evaluator in which all the read-only data-structures are
// shared with the receiver and the temporary buffers are reallocated. The receiver and the returned
// Evaluators can be used concurrently.
func (eval *Evaluator) ShallowCopy() *Evaluator {
return &Evaluator{*eval.Evaluator.ShallowCopy(), eval.params}
}
// WithKey creates a shallow copy of the receiver Evaluator for which the new EvaluationKey is evaluationKey
// and where the temporary buffers are shared. The receiver and the returned Evaluators cannot be used concurrently.
func (eval *Evaluator) WithKey(evaluationKey *rlwe.EvaluationKey) *Evaluator {
return &Evaluator{*eval.Evaluator.WithKey(evaluationKey), eval.params}
}
// ExternalProduct computes RLWE x RGSW -> RLWE
//
// RLWE : (-as + m + e, a)
// x
// RGSW : [(-as + P*w*m1 + e, a), (-bs + e, b + P*w*m1)]
// =
// RLWE : (<RLWE, RGSW[0]>, <RLWE, RGSW[1]>)
func (eval *Evaluator) ExternalProduct(op0 *rlwe.Ciphertext, op1 *Ciphertext, op2 *rlwe.Ciphertext) {
levelQ, levelP := op1.LevelQ(), op1.LevelP()
var c0QP, c1QP ringqp.Poly
if op0 == op2 {
c0QP, c1QP = eval.BuffQP[1], eval.BuffQP[2]
} else {
c0QP, c1QP = ringqp.Poly{Q: op2.Value[0], P: eval.BuffQP[1].P}, ringqp.Poly{Q: op2.Value[1], P: eval.BuffQP[2].P}
}
if levelP < 1 {
// If log(Q) * (Q-1)**2 < 2^{64}-1
if ringQ := eval.params.RingQ(); levelQ == 0 && levelP == -1 && (ringQ.Modulus[0]>>29) == 0 {
eval.externalProduct32Bit(op0, op1, c0QP.Q, c1QP.Q)
q, mredParams := ringQ.Modulus[0], ringQ.MredParams[0]
ring.InvMFormVec(c0QP.Q.Coeffs[0], op2.Value[0].Coeffs[0], q, mredParams)
ring.InvMFormVec(c1QP.Q.Coeffs[0], op2.Value[1].Coeffs[0], q, mredParams)
} else {
eval.externalProductInPlaceSinglePAndBitDecomp(op0, op1, c0QP, c1QP)
if levelP == 0 {
eval.BasisExtender.ModDownQPtoQNTT(levelQ, levelP, c0QP.Q, c0QP.P, op2.Value[0])
eval.BasisExtender.ModDownQPtoQNTT(levelQ, levelP, c1QP.Q, c1QP.P, op2.Value[1])
} else {
op2.Value[0].CopyValues(c0QP.Q)
op2.Value[1].CopyValues(c1QP.Q)
}
}
} else {
eval.externalProductInPlaceMultipleP(levelQ, levelP, op0, op1, eval.BuffQP[1].Q, eval.BuffQP[1].P, eval.BuffQP[2].Q, eval.BuffQP[2].P)
eval.BasisExtender.ModDownQPtoQNTT(levelQ, levelP, c0QP.Q, c0QP.P, op2.Value[0])
eval.BasisExtender.ModDownQPtoQNTT(levelQ, levelP, c1QP.Q, c1QP.P, op2.Value[1])
}
}
func (eval *Evaluator) externalProduct32Bit(ct0 *rlwe.Ciphertext, rgsw *Ciphertext, c0, c1 *ring.Poly) {
// rgsw = [(-as + P*w*m1 + e, a), (-bs + e, b + P*w*m1)]
// ct = [-cs + m0 + e, c]
// ctOut = [<ct, rgsw[0]>, <ct, rgsw[1]>] = [ct[0] * rgsw[0][0] + ct[1] * rgsw[0][1], ct[0] * rgsw[1][0] + ct[1] * rgsw[1][1]]
ringQ := eval.params.RingQ()
pw2 := eval.params.Pow2Base()
mask := uint64(((1 << pw2) - 1))
cw := eval.BuffQP[0].Q.Coeffs[0]
cwNTT := eval.BuffBitDecomp
acc0 := c0.Coeffs[0]
acc1 := c1.Coeffs[0]
// (a, b) + (c0 * rgsw[0][0], c0 * rgsw[0][1])
// (a, b) + (c1 * rgsw[1][0], c1 * rgsw[1][1])
for i, el := range rgsw.Value {
ringQ.InvNTTLvl(0, ct0.Value[i], eval.BuffInvNTT)
for j := range el.Value[0] {
ring.MaskVec(eval.BuffInvNTT.Coeffs[0], cw, j*pw2, mask)
if j == 0 && i == 0 {
ringQ.NTTSingleLazy(0, cw, cwNTT)
ring.MulCoeffsNoModVec(el.Value[0][j].Value[0].Q.Coeffs[0], cwNTT, acc0)
ring.MulCoeffsNoModVec(el.Value[0][j].Value[1].Q.Coeffs[0], cwNTT, acc1)
} else {
ringQ.NTTSingleLazy(0, cw, cwNTT)
ring.MulCoeffsNoModAndAddNoModVec(el.Value[0][j].Value[0].Q.Coeffs[0], cwNTT, acc0)
ring.MulCoeffsNoModAndAddNoModVec(el.Value[0][j].Value[1].Q.Coeffs[0], cwNTT, acc1)
}
}
}
}
func (eval *Evaluator) externalProductInPlaceSinglePAndBitDecomp(ct0 *rlwe.Ciphertext, rgsw *Ciphertext, c0QP, c1QP ringqp.Poly) {
// rgsw = [(-as + P*w*m1 + e, a), (-bs + e, b + P*w*m1)]
// ct = [-cs + m0 + e, c]
// ctOut = [<ct, rgsw[0]>, <ct, rgsw[1]>] = [ct[0] * rgsw[0][0] + ct[1] * rgsw[0][1], ct[0] * rgsw[1][0] + ct[1] * rgsw[1][1]]
ringQ := eval.params.RingQ()
ringP := eval.params.RingP()
levelQ := rgsw.LevelQ()
levelP := rgsw.LevelP()
pw2 := eval.params.Pow2Base()
mask := uint64(((1 << pw2) - 1))
if mask == 0 {
mask = 0xFFFFFFFFFFFFFFFF
}
decompRNS := eval.params.DecompRNS(levelQ, levelP)
decompPw2 := eval.params.DecompPw2(levelQ, levelP)
// (a, b) + (c0 * rgsw[k][0], c0 * rgsw[k][1])
for k, el := range rgsw.Value {
ringQ.InvNTTLvl(levelQ, ct0.Value[k], eval.BuffInvNTT)
cw := eval.BuffQP[0].Q.Coeffs[0]
cwNTT := eval.BuffBitDecomp
for i := 0; i < decompRNS; i++ {
for j := 0; j < decompPw2; j++ {
ring.MaskVec(eval.BuffInvNTT.Coeffs[i], cw, j*pw2, mask)
if k == 0 && i == 0 && j == 0 {
for u := 0; u < levelQ+1; u++ {
ringQ.NTTSingleLazy(u, cw, cwNTT)
ring.MulCoeffsMontgomeryVec(el.Value[i][j].Value[0].Q.Coeffs[u], cwNTT, c0QP.Q.Coeffs[u], ringQ.Modulus[u], ringQ.MredParams[u])
ring.MulCoeffsMontgomeryVec(el.Value[i][j].Value[1].Q.Coeffs[u], cwNTT, c1QP.Q.Coeffs[u], ringQ.Modulus[u], ringQ.MredParams[u])
}
for u := 0; u < levelP+1; u++ {
ringP.NTTSingleLazy(u, cw, cwNTT)
ring.MulCoeffsMontgomeryVec(el.Value[i][j].Value[0].P.Coeffs[u], cwNTT, c0QP.P.Coeffs[u], ringP.Modulus[u], ringP.MredParams[u])
ring.MulCoeffsMontgomeryVec(el.Value[i][j].Value[1].P.Coeffs[u], cwNTT, c1QP.P.Coeffs[u], ringP.Modulus[u], ringP.MredParams[u])
}
} else {
for u := 0; u < levelQ+1; u++ {
ringQ.NTTSingleLazy(u, cw, cwNTT)
ring.MulCoeffsMontgomeryAndAddVec(el.Value[i][j].Value[0].Q.Coeffs[u], cwNTT, c0QP.Q.Coeffs[u], ringQ.Modulus[u], ringQ.MredParams[u])
ring.MulCoeffsMontgomeryAndAddVec(el.Value[i][j].Value[1].Q.Coeffs[u], cwNTT, c1QP.Q.Coeffs[u], ringQ.Modulus[u], ringQ.MredParams[u])
}
for u := 0; u < levelP+1; u++ {
ringP.NTTSingleLazy(u, cw, cwNTT)
ring.MulCoeffsMontgomeryAndAddVec(el.Value[i][j].Value[0].P.Coeffs[u], cwNTT, c0QP.P.Coeffs[u], ringP.Modulus[u], ringP.MredParams[u])
ring.MulCoeffsMontgomeryAndAddVec(el.Value[i][j].Value[1].P.Coeffs[u], cwNTT, c1QP.P.Coeffs[u], ringP.Modulus[u], ringP.MredParams[u])
}
}
}
}
}
}
func (eval *Evaluator) externalProductInPlaceMultipleP(levelQ, levelP int, ct0 *rlwe.Ciphertext, rgsw *Ciphertext, c0OutQ, c0OutP, c1OutQ, c1OutP *ring.Poly) {
var reduce int
ringQ := eval.params.RingQ()
ringP := eval.params.RingP()
ringQP := eval.params.RingQP()
c2QP := eval.BuffQP[0]
c0QP := ringqp.Poly{Q: c0OutQ, P: c0OutP}
c1QP := ringqp.Poly{Q: c1OutQ, P: c1OutP}
decompRNS := eval.params.DecompRNS(levelQ, levelP)
QiOverF := eval.params.QiOverflowMargin(levelQ) >> 1
PiOverF := eval.params.PiOverflowMargin(levelP) >> 1
var c2NTT, c2InvNTT *ring.Poly
for k, el := range rgsw.Value {
if ct0.IsNTT {
c2NTT = ct0.Value[k]
c2InvNTT = eval.BuffInvNTT
ringQ.InvNTTLvl(levelQ, c2NTT, c2InvNTT)
} else {
c2NTT = eval.BuffInvNTT
c2InvNTT = ct0.Value[k]
ringQ.NTTLvl(levelQ, c2InvNTT, c2NTT)
}
// (a, b) + (c0 * rgsw[0][0], c0 * rgsw[0][1])
for i := 0; i < decompRNS; i++ {
eval.DecomposeSingleNTT(levelQ, levelP, levelP+1, i, c2NTT, c2InvNTT, c2QP.Q, c2QP.P)
if k == 0 && i == 0 {
ringQP.MulCoeffsMontgomeryConstantLvl(levelQ, levelP, el.Value[i][0].Value[0], c2QP, c0QP)
ringQP.MulCoeffsMontgomeryConstantLvl(levelQ, levelP, el.Value[i][0].Value[1], c2QP, c1QP)
} else {
ringQP.MulCoeffsMontgomeryConstantAndAddNoModLvl(levelQ, levelP, el.Value[i][0].Value[0], c2QP, c0QP)
ringQP.MulCoeffsMontgomeryConstantAndAddNoModLvl(levelQ, levelP, el.Value[i][0].Value[1], c2QP, c1QP)
}
if reduce%QiOverF == QiOverF-1 {
ringQ.ReduceLvl(levelQ, c0QP.Q, c0QP.Q)
ringQ.ReduceLvl(levelQ, c1QP.Q, c1QP.Q)
}
if reduce%PiOverF == PiOverF-1 {
ringP.ReduceLvl(levelP, c0QP.P, c0QP.P)
ringP.ReduceLvl(levelP, c1QP.P, c1QP.P)
}
reduce++
}
}
if reduce%QiOverF != 0 {
ringQ.ReduceLvl(levelQ, c0QP.Q, c0QP.Q)
ringQ.ReduceLvl(levelQ, c1QP.Q, c1QP.Q)
}
if reduce%PiOverF != 0 {
ringP.ReduceLvl(levelP, c0QP.P, c0QP.P)
ringP.ReduceLvl(levelP, c1QP.P, c1QP.P)
}
}
// AddNoModLvl adds op to ctOut, without modular reduction.
func AddNoModLvl(levelQ, levelP int, op interface{}, ringQP ringqp.Ring, ctOut *Ciphertext) {
switch el := op.(type) {
case *Plaintext:
nQ := levelQ + 1
nP := levelP + 1
if nP == 0 {
nP = 1
}
for i := range ctOut.Value[0].Value {
for j := range ctOut.Value[0].Value[i] {
start, end := i*nP, (i+1)*nP
if end > nQ {
end = nQ
}
for k := start; k < end; k++ {
ring.AddVecNoMod(ctOut.Value[0].Value[i][j].Value[0].Q.Coeffs[k], el.Value[j].Coeffs[k], ctOut.Value[0].Value[i][j].Value[0].Q.Coeffs[k])
ring.AddVecNoMod(ctOut.Value[1].Value[i][j].Value[1].Q.Coeffs[k], el.Value[j].Coeffs[k], ctOut.Value[1].Value[i][j].Value[1].Q.Coeffs[k])
}
}
}
case *Ciphertext:
for i := range el.Value[0].Value {
for j := range el.Value[0].Value[i] {
ringQP.AddNoModLvl(levelQ, levelP, ctOut.Value[0].Value[i][j].Value[0], el.Value[0].Value[i][j].Value[0], ctOut.Value[0].Value[i][j].Value[0])
ringQP.AddNoModLvl(levelQ, levelP, ctOut.Value[0].Value[i][j].Value[1], el.Value[0].Value[i][j].Value[1], ctOut.Value[0].Value[i][j].Value[1])
ringQP.AddNoModLvl(levelQ, levelP, ctOut.Value[1].Value[i][j].Value[0], el.Value[1].Value[i][j].Value[0], ctOut.Value[1].Value[i][j].Value[0])
ringQP.AddNoModLvl(levelQ, levelP, ctOut.Value[1].Value[i][j].Value[1], el.Value[1].Value[i][j].Value[1], ctOut.Value[1].Value[i][j].Value[1])
}
}
default:
panic("cannot AddNoModLvl: unsuported op.(type), must be either *rgsw.Plaintext or *rgsw.Ciphertext")
}
}
// ReduceLvl applies the modular reduction on ctIn and returns the result on ctOut.
func ReduceLvl(levelQ, levelP int, ctIn *Ciphertext, ringQP ringqp.Ring, ctOut *Ciphertext) {
for i := range ctIn.Value[0].Value {
for j := range ctIn.Value[0].Value[i] {
ringQP.ReduceLvl(levelQ, levelP, ctIn.Value[0].Value[i][j].Value[0], ctOut.Value[0].Value[i][j].Value[0])
ringQP.ReduceLvl(levelQ, levelP, ctIn.Value[0].Value[i][j].Value[1], ctOut.Value[0].Value[i][j].Value[1])
ringQP.ReduceLvl(levelQ, levelP, ctIn.Value[1].Value[i][j].Value[0], ctOut.Value[1].Value[i][j].Value[0])
ringQP.ReduceLvl(levelQ, levelP, ctIn.Value[1].Value[i][j].Value[1], ctOut.Value[1].Value[i][j].Value[1])
}
}
}
// MulByXPowAlphaMinusOneConstantLvl multiplies ctOut by (X^alpha - 1) and returns the result on ctOut.
func MulByXPowAlphaMinusOneConstantLvl(levelQ, levelP int, ctIn *Ciphertext, powXMinusOne ringqp.Poly, ringQP ringqp.Ring, ctOut *Ciphertext) {
for i := range ctIn.Value[0].Value {
for j := range ctIn.Value[0].Value[i] {
ringQP.MulCoeffsMontgomeryConstantLvl(levelQ, levelP, ctIn.Value[0].Value[i][j].Value[0], powXMinusOne, ctOut.Value[0].Value[i][j].Value[0])
ringQP.MulCoeffsMontgomeryConstantLvl(levelQ, levelP, ctIn.Value[0].Value[i][j].Value[1], powXMinusOne, ctOut.Value[0].Value[i][j].Value[1])
ringQP.MulCoeffsMontgomeryConstantLvl(levelQ, levelP, ctIn.Value[1].Value[i][j].Value[0], powXMinusOne, ctOut.Value[1].Value[i][j].Value[0])
ringQP.MulCoeffsMontgomeryConstantLvl(levelQ, levelP, ctIn.Value[1].Value[i][j].Value[1], powXMinusOne, ctOut.Value[1].Value[i][j].Value[1])
}
}
}
// MulByXPowAlphaMinusOneAndAddNoModLvl multiplies ctOut by (X^alpha - 1) and adds the result on ctOut.
func MulByXPowAlphaMinusOneAndAddNoModLvl(levelQ, levelP int, ctIn *Ciphertext, powXMinusOne ringqp.Poly, ringQP ringqp.Ring, ctOut *Ciphertext) {
for i := range ctIn.Value[0].Value {
for j := range ctIn.Value[0].Value[i] {
ringQP.MulCoeffsMontgomeryConstantAndAddNoModLvl(levelQ, levelP, ctIn.Value[0].Value[i][j].Value[0], powXMinusOne, ctOut.Value[0].Value[i][j].Value[0])
ringQP.MulCoeffsMontgomeryConstantAndAddNoModLvl(levelQ, levelP, ctIn.Value[0].Value[i][j].Value[1], powXMinusOne, ctOut.Value[0].Value[i][j].Value[1])
ringQP.MulCoeffsMontgomeryConstantAndAddNoModLvl(levelQ, levelP, ctIn.Value[1].Value[i][j].Value[0], powXMinusOne, ctOut.Value[1].Value[i][j].Value[0])
ringQP.MulCoeffsMontgomeryConstantAndAddNoModLvl(levelQ, levelP, ctIn.Value[1].Value[i][j].Value[1], powXMinusOne, ctOut.Value[1].Value[i][j].Value[1])
}
}
}