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scheme-switching.py
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scheme-switching.py
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from openfhe import *
from math import *
def main():
SwitchCKKSToFHEW()
SwitchFHEWtoCKKS()
FloorViaSchemeSwitching()
FuncViaSchemeSwitching()
PolyViaSchemeSwitching()
ComparisonViaSchemeSwitching()
ArgminViaSchemeSwitching()
ArgminViaSchemeSwitchingAlt()
ArgminViaSchemeSwitchingUnit()
ArgminViaSchemeSwitchingAltUnit()
def SwitchCKKSToFHEW():
# Example of switching a packed ciphertext from CKKS to multiple FHEW ciphertexts.
print("\n-----SwitchCKKSToFHEW-----\n")
# Step 1: Setup CryptoContext for CKKS
# Specify main parameters
multDepth = 3
firstModSize = 60
scaleModSize = 50
ringDim = 4096
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 25
# slots = ringDim / 2 # Uncomment for fully-packed
slots = 16 # sparsely-packed
batchSize = slots
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetFirstModSize(firstModSize)
parameters.SetScalingModSize(scaleModSize)
parameters.SetScalingTechnique(FIXEDMANUAL)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
cc = GenCryptoContext(parameters)
# Enable the features that you wish to use
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(SCHEMESWITCH)
print(f"CKKS scheme is using ring dimension {cc.GetRingDimension()},")
print(f"number of slots {slots}, and supports a multiplicative depth of {multDepth}\n")
# Generate encryption keys
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
# FHEWparams = cc.EvalCKKStoFHEWSetup(sl, slBin, False, logQ_ccLWE, False, slots)
params = SchSwchParams()
params.SetSecurityLevelCKKS(sl)
params.SetSecurityLevelFHEW(slBin)
params.SetCtxtModSizeFHEWLargePrec(logQ_ccLWE)
params.SetNumSlotsCKKS(slots)
privateKeyFHEW = cc.EvalCKKStoFHEWSetup(params)
ccLWE = cc.GetBinCCForSchemeSwitch()
# ccLWE = FHEWparams[0]
# privateKeyFHEW = FHEWparams[1]
cc.EvalCKKStoFHEWKeyGen(keys, privateKeyFHEW)
print(f"FHEW scheme is using a lattice parameter {ccLWE.Getn()},")
print(f"logQ {logQ_ccLWE},")
print(f"and modulus q {ccLWE.Getq()}\n")
# Compute the scaling factor to decrypt correctly in FHEW; the LWE mod switch is performed on the ciphertext at the last level
pLWE1 = ccLWE.GetMaxPlaintextSpace() # Small precision
modulus_LWE = 1 << logQ_ccLWE
beta = ccLWE.GetBeta()
pLWE2 = modulus_LWE / (2*beta) # Large precision
scale1 = 1 / pLWE1
scale2 = 1 / pLWE2
# Perform the precomputation for switching
cc.EvalCKKStoFHEWPrecompute(scale1)
# Step 3: Encoding and encryption of inputs
# Inputs
x1 = [0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
x2 = [0.0, 271.1, 30000.0, pLWE2-2]
encodedLength1 = len(x1)
encodedLength2 = len(x2)
# Encoding as plaintexts
ptxt1 = cc.MakeCKKSPackedPlaintext(x1, 1, 0)
ptxt2 = cc.MakeCKKSPackedPlaintext(x2, 1, 0)
# Encrypt the encoded vectors
c1 = cc.Encrypt(keys.publicKey, ptxt1)
c2 = cc.Encrypt(keys.publicKey, ptxt2)
# Step 4: Scheme Switching from CKKS to FHEW
cTemp = cc.EvalCKKStoFHEW(c1, encodedLength1)
print(f"\n---Decrypting switched ciphertext with small precision (plaintext modulus {pLWE1}) ---\n")
x1Int = [round(x) % pLWE1 for x in x1]
ptxt1.SetLength(encodedLength1)
print(f"Input x1: {ptxt1.GetRealPackedValue()}; which rounds to {x1Int}")
print("FHEW Decryption")
for i in range(len(cTemp)):
result = ccLWE.Decrypt(privateKeyFHEW, cTemp[i], pLWE1)
print(result, end=" ")
print("\n")
# B: Second scheme switching case
# Perform the precomputation for switching
cc.EvalCKKStoFHEWPrecompute(scale2)
# Transform the ciphertext from CKKS to FHEW (only for the number of inputs given)
cTemp2 = cc.EvalCKKStoFHEW(c2, encodedLength2)
print(f"\n---Decrypting switched ciphertext with large precision (plaintext modulus {pLWE2}) ---\n")
ptxt2.SetLength(encodedLength2)
print(f"Input x2: {ptxt2.GetRealPackedValue()}")
print("FHEW Decryption")
for i in range(len(cTemp2)):
result = ccLWE.Decrypt(privateKeyFHEW, cTemp2[i], int(pLWE2))
print(result, end=" ")
print("\n")
# C: Decompose the FHEW ciphertexts in smaller digits
print(f"Decomposed values for digit size of {pLWE1}:")
# Generate the bootstrapping keys (refresh and switching keys)
ccLWE.BTKeyGen(privateKeyFHEW)
for j in range(len(cTemp2)):
# Decompose the large ciphertext into small ciphertexts that fit in q
decomp = ccLWE.EvalDecomp(cTemp2[j])
# Decryption
p = ccLWE.GetMaxPlaintextSpace()
for i in range(len(decomp)):
ct = decomp[i]
if i == len(decomp) - 1:
p = int(pLWE2 / (pLWE1 ** floor(log(pLWE2)/log(pLWE1))))
# The last digit should be up to P / p^floor(log_p(P))
resultDecomp = ccLWE.Decrypt(privateKeyFHEW, ct, p)
print(f"( {resultDecomp} * {pLWE1} ^ {i} )")
if i != len(decomp) - 1:
print("+", end=" ")
print("\n")
def SwitchFHEWtoCKKS():
print("\n-----SwitchFHEWtoCKKS-----\n")
print("Output precision is only wrt the operations in CKKS after switching back.\n")
# Step 1: Setup CryptoContext for CKKS to be switched into
# A. Specify main parameters
scTech = FIXEDAUTO
multDepth = 3 + 9 + 1
# for r = 3 in FHEWtoCKKS, Chebyshev max depth allowed is 9, 1 more level for postscaling
if scTech == FLEXIBLEAUTOEXT:
multDepth += 1
scaleModSize = 50
ringDim = 8192
sl = HEStd_NotSet # If this is not HEStd_NotSet, ensure ringDim is compatible
logQ_ccLWE = 28
# slots = ringDim/2; # Uncomment for fully-packed
slots = 16 # sparsely-packed
batchSize = slots
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetScalingModSize(scaleModSize)
parameters.SetScalingTechnique(scTech)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
cc = GenCryptoContext(parameters)
# Enable the features that you wish to use
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(ADVANCEDSHE)
cc.Enable(SCHEMESWITCH)
print(f"CKKS scheme is using ring dimension {cc.GetRingDimension()},\n number of slots {slots}, and suports a multiplicative depth of {multDepth}\n")
# Generate encryption keys
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
ccLWE = BinFHEContext()
ccLWE.GenerateBinFHEContext(TOY, False, logQ_ccLWE, 0, GINX, False)
# LWE private key
lwesk = ccLWE.KeyGen()
print(f"FHEW scheme is using lattice parameter {ccLWE.Getn()},\n logQ {logQ_ccLWE},\n and modulus q {ccLWE.Getq()}\n")
# Step 3. Precompute the necessary keys and information for switching from FHEW to CKKS
cc.EvalFHEWtoCKKSSetup(ccLWE, slots, logQ_ccLWE)
cc.EvalFHEWtoCKKSKeyGen(keys, lwesk)
# Step 4: Encoding and encryption of inputs
# For correct CKKS decryption, the messages have to be much smaller than the FHEW plaintext modulus!
pLWE1 = ccLWE.GetMaxPlaintextSpace() # Small precision
pLWE2 = 256 # Medium precision
modulus_LWE = 1 << logQ_ccLWE
beta = ccLWE.GetBeta()
pLWE3 = int(modulus_LWE / (2 * beta)) # Large precision
x1 = [1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0]
x2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
if len(x1) < slots:
zeros = [0] * (slots - len(x1))
x1.extend(zeros)
x2.extend(zeros)
# Encrypt
# Encrypted under small plaintext modulus p = 4 and ciphertext modulus:
ctxtsLWE1 = [ccLWE.Encrypt(lwesk, x1[i]) for i in range(slots)]
# Encrypted under larger plaintext modulus p = 16 but small ciphertext modulus:
ctxtsLWE2 = [ccLWE.Encrypt(lwesk, x1[i], FRESH, pLWE1) for i in range(slots)]
# Encrypted under larger plaintext modulus and large ciphertext modulus:
ctxtsLWE3 = [ccLWE.Encrypt(lwesk, x2[i], FRESH, pLWE2, modulus_LWE) for i in range(slots)]
# Encrypted under large plaintext modulus and large ciphertext modulus:
ctxtsLWE4 = [ccLWE.Encrypt(lwesk, x2[i], FRESH, pLWE3, modulus_LWE) for i in range(slots)]
# Step 5. Perform the scheme switching
cTemp = cc.EvalFHEWtoCKKS(ctxtsLWE1, slots, slots)
print(f"\n---Input x1: {x1} encrypted under p = 4 and Q = {ctxtsLWE1[0].GetModulus()} ---")
# Step 6. Decrypt
plaintextDec = cc.Decrypt(keys.secretKey, cTemp)
plaintextDec.SetLength(slots)
print(f"Switched CKKS decryption 1: {plaintextDec}")
# Step 5'. Perform the scheme switching
cTemp = cc.EvalFHEWtoCKKS(ctxtsLWE2, slots, slots, pLWE1, 0, pLWE1)
print(f"\n---Input x1: {x1} encrypted under p = {pLWE1} and Q = {ctxtsLWE2[0].GetModulus()} ---")
# Step 6'. Decrypt
plaintextDec = cc.Decrypt(keys.secretKey, cTemp)
plaintextDec.SetLength(slots)
print(f"Switched CKKS decryption 2: {plaintextDec}")
# Step 5''. Perform the scheme switching
cTemp = cc.EvalFHEWtoCKKS(ctxtsLWE3, slots, slots, pLWE2, 0, pLWE2)
print(f"\n---Input x2: {x2} encrypted under p = {pLWE2} and Q = {ctxtsLWE3[0].GetModulus()} ---")
# Step 6''. Decrypt
plaintextDec = cc.Decrypt(keys.secretKey, cTemp)
plaintextDec.SetLength(slots)
print(f"Switched CKKS decryption 3: {plaintextDec}")
# Step 5'''. Perform the scheme switching
cTemp2 = cc.EvalFHEWtoCKKS(ctxtsLWE4, slots, slots, pLWE3, 0, pLWE3)
print(f"\n---Input x2: {x2} encrypted under p = {pLWE3} and Q = {ctxtsLWE4[0].GetModulus()} ---")
# Step 6'''. Decrypt
plaintextDec = cc.Decrypt(keys.secretKey, cTemp2)
plaintextDec.SetLength(slots)
print(f"Switched CKKS decryption 4: {plaintextDec}")
def FloorViaSchemeSwitching():
print("\n-----FloorViaSchemeSwitching-----\n")
print("Output precision is only wrt the operations in CKKS after switching back.\n")
# Step 1: Setup CryptoContext for CKKS
scTech = FIXEDAUTO
multDepth = 3 + 9 + 1 # for r = 3 in FHEWtoCKKS, Chebyshev max depth allowed is 9, 1 more level for postscaling
if scTech == FLEXIBLEAUTOEXT:
multDepth += 1
scaleModSize = 50
ringDim = 8192
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 23
slots = 16 # sparsely-packed
batchSize = slots
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetScalingModSize(scaleModSize)
parameters.SetScalingTechnique(scTech)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
cc = GenCryptoContext(parameters)
# Enable the features that you wish to use
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(ADVANCEDSHE)
cc.Enable(SCHEMESWITCH)
print(f"CKKS scheme is using ring dimension {cc.GetRingDimension()},\n number of slots {slots}, and suports a multiplicative depth of {multDepth}\n")
# Generate encryption keys.
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
params = SchSwchParams()
params.SetSecurityLevelCKKS(sl)
params.SetSecurityLevelFHEW(slBin)
params.SetCtxtModSizeFHEWLargePrec(logQ_ccLWE)
params.SetNumSlotsCKKS(slots)
params.SetNumValues(slots)
privateKeyFHEW = cc.EvalSchemeSwitchingSetup(params)
ccLWE = cc.GetBinCCForSchemeSwitch()
cc.EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW)
# Generate bootstrapping key for EvalFloor
ccLWE.BTKeyGen(privateKeyFHEW)
print(f"FHEW scheme is using lattice parameter {ccLWE.Getn()},\n logQ {logQ_ccLWE},\n and modulus q {ccLWE.Getq()}\n")
# Set the scaling factor to be able to decrypt; the LWE mod switch is performed on the ciphertext at the last level
modulus_CKKS_from = cc.GetModulusCKKS()
modulus_LWE = 1 << logQ_ccLWE
beta = ccLWE.GetBeta()
pLWE = int(modulus_LWE / (2 * beta)) # Large precision
scaleCF = 1.0 / pLWE
cc.EvalCKKStoFHEWPrecompute(scaleCF)
# Step 3: Encoding and encryption of inputs
# Inputs
x1 = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0]
# Encoding as plaintexts
ptxt1 = cc.MakeCKKSPackedPlaintext(x1, 1, 0, None)#, None)
# Encrypt the encoded vectors
c1 = cc.Encrypt(keys.publicKey, ptxt1)
# Step 4: Scheme switching from CKKS to FHEW
cTemp = cc.EvalCKKStoFHEW(c1, slots)
# Step 5: Evaluate the floor function
bits = 2
cFloor = [ccLWE.EvalFloor(cTemp[i], bits) for i in range(len(cTemp))]
print(f"Input x1: {ptxt1.GetRealPackedValue()}")
print(f"Expected result for EvalFloor with {bits} bits: ", end="")
for i in range(slots):
print(int(ptxt1.GetRealPackedValue()[i]) >> bits, end=" ")
print(f"\nFHEW decryption p = {pLWE}/(1 << bits) = {pLWE // (1 << bits)}: ", end="")
for i in range(len(cFloor)):
pFloor = ccLWE.Decrypt(privateKeyFHEW, cFloor[i], pLWE // (1 << bits))
print(pFloor, end=" ")
print("\n")
# Step 6: Scheme switching from FHEW to CKKS
cTemp2 = cc.EvalFHEWtoCKKS(cFloor, slots, slots, pLWE // (1 << bits), 0, pLWE / (1 << bits))
plaintextDec2 = cc.Decrypt(keys.secretKey, cTemp2)
plaintextDec2.SetLength(slots)
print(f"Switched floor decryption modulus_LWE mod {pLWE // (1 << bits)}: {plaintextDec2}")
def FuncViaSchemeSwitching():
print("\n-----FuncViaSchemeSwitching-----\n")
print("Output precision is only wrt the operations in CKKS after switching back.\n")
# Step 1: Setup CryptoContext for CKKS
multDepth = 9 + 3 + 2 # 1 for CKKS to FHEW, 14 for FHEW to CKKS
scaleModSize = 50
ringDim = 2048
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 25
arbFunc = True
slots = 8 # sparsely-packed
batchSize = slots
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetScalingModSize(scaleModSize)
parameters.SetScalingTechnique(FIXEDMANUAL)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
cc = GenCryptoContext(parameters)
# Enable the features that you wish to use
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(ADVANCEDSHE)
cc.Enable(SCHEMESWITCH)
print(f"CKKS scheme is using ring dimension {cc.GetRingDimension()},\n and number of slots {slots}\n")
# Generate encryption keys.
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
params = SchSwchParams()
params.SetSecurityLevelCKKS(sl)
params.SetSecurityLevelFHEW(slBin)
params.SetArbitraryFunctionEvaluation(True)
params.SetCtxtModSizeFHEWLargePrec(logQ_ccLWE)
params.SetNumSlotsCKKS(slots)
params.SetNumValues(slots)
privateKeyFHEW = cc.EvalSchemeSwitchingSetup(params)
ccLWE = cc.GetBinCCForSchemeSwitch()
cc.EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW)
# Generate the bootstrapping keys for EvalFunc in FHEW
ccLWE.BTKeyGen(privateKeyFHEW)
print(f"FHEW scheme is using lattice parameter {ccLWE.Getn()},\n logQ {logQ_ccLWE},\n and modulus q {ccLWE.Getq()}\n")
# Set the scaling factor to be able to decrypt; the LWE mod switch is performed on the ciphertext at the last level
pLWE = ccLWE.GetMaxPlaintextSpace() # Small precision because GenerateLUTviaFunction needs p < q
scaleCF = 1.0 / pLWE
cc.EvalCKKStoFHEWPrecompute(scaleCF)
# Step 3: Initialize the function
# Initialize Function f(x) = x^3 + 2x + 1 % p
def fp(m, p1):
if m < p1:
return (m * m * m + 2 * m * m + 1) % p1
else:
return ((m - p1 / 2) * (m - p1 / 2) * (m - p1 / 2) + 2 * (m - p1 / 2) * (m - p1 / 2) + 1) % p1
# Generate LUT from function f(x)
lut = ccLWE.GenerateLUTviaFunction(fp, pLWE)
# Step 4: Encoding and encryption of inputs
# Inputs
x1 = [0.0, 0.3, 2.0, 4.0, 5.0, 6.0, 7.0, 8.0]
# Encoding as plaintexts
ptxt1 = cc.MakeCKKSPackedPlaintext(x1, 1, 0, None)
# Encrypt the encoded vectors
c1 = cc.Encrypt(keys.publicKey, ptxt1)
# Step 5: Scheme switching from CKKS to FHEW
cTemp = cc.EvalCKKStoFHEW(c1, slots)
print(f"Input x1: {ptxt1.GetRealPackedValue()}")
print("FHEW decryption: ", end="")
for i in range(len(cTemp)):
result = ccLWE.Decrypt(privateKeyFHEW, cTemp[i], pLWE)
print(result, end=" ")
# Step 6: Evaluate the function
cFunc = [ccLWE.EvalFunc(cTemp[i], lut) for i in range(len(cTemp))]
print("\nExpected result x^3 + 2*x + 1 mod p: ", end="")
for i in range(slots):
print(fp(int(x1[i]) % pLWE, pLWE), end=" ")
print(f"\nFHEW decryption mod {pLWE}: ", end="")
for i in range(len(cFunc)):
pFunc = ccLWE.Decrypt(privateKeyFHEW, cFunc[i], pLWE)
print(pFunc, end=" ")
print("\n")
# Step 7: Scheme switching from FHEW to CKKS
cTemp2 = cc.EvalFHEWtoCKKS(cFunc, slots, slots, pLWE, 0, pLWE)
plaintextDec2 = cc.Decrypt(keys.secretKey, cTemp2)
plaintextDec2.SetLength(slots)
print(f"\nSwitched decryption modulus_LWE mod {pLWE}\nworks only for messages << p: {plaintextDec2}")
# Transform through arcsine
cTemp2 = cc.EvalFHEWtoCKKS(cFunc, slots, slots, 4, 0, 2)
plaintextDec2 = cc.Decrypt(keys.secretKey, cTemp2)
plaintextDec2.SetLength(slots)
print("Arcsin(switched result) * p/2pi gives the correct result if messages are < p/4: ", end="")
for i in range(slots):
x = max(min(plaintextDec2.GetRealPackedValue()[i], 1.0), -1.0)
print(asin(x) * pLWE / (2 * pi), end=" ")
print()
def PolyViaSchemeSwitching():
print("\n-----PolyViaSchemeSwitching-----\n")
# Step 1: Setup CryptoContext for CKKS to be switched into
# A. Specify main parameters
scTech = FIXEDAUTO
multDepth = 3 + 9 + 1 + 2 # for r = 3 in FHEWtoCKKS, Chebyshev max depth allowed is 9, 1 more level for postscaling, 3 levels for functionality
if scTech == FLEXIBLEAUTOEXT:
multDepth += 1
scaleModSize = 50
ringDim = 2048
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 25
slots = 16 # sparsely-packed
batchSize = slots
# Create encryption parameters
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetScalingModSize(scaleModSize)
parameters.SetScalingTechnique(scTech)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
cc = GenCryptoContext(parameters)
# Enable the features that you wish to use
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(ADVANCEDSHE)
cc.Enable(SCHEMESWITCH)
print(f"CKKS scheme is using ring dimension {cc.GetRingDimension()},\n number of slots {slots}, and suports a multiplicative depth of {multDepth}\n")
# Generate encryption keys
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
params = SchSwchParams()
params.SetSecurityLevelCKKS(sl)
params.SetSecurityLevelFHEW(slBin)
params.SetCtxtModSizeFHEWLargePrec(logQ_ccLWE)
params.SetNumSlotsCKKS(slots)
params.SetNumValues(slots)
privateKeyFHEW = cc.EvalSchemeSwitchingSetup(params)
ccLWE = cc.GetBinCCForSchemeSwitch()
cc.EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW)
print(f"FHEW scheme is using lattice parameter {ccLWE.Getn()},\n logQ {logQ_ccLWE},\n and modulus q {ccLWE.Getq()}\n")
pLWE1 = ccLWE.GetMaxPlaintextSpace() # Small precision
modulus_LWE = 1 << logQ_ccLWE
beta = ccLWE.GetBeta()
pLWE2 = int(modulus_LWE / (2 * beta)) # Large precision
scale1 = 1.0 / pLWE1
scale2 = 1.0 / pLWE2
# Generate keys for the CKKS intermediate computation
cc.EvalMultKeyGen(keys.secretKey)
cc.EvalRotateKeyGen(keys.secretKey, [1,2])
# Step 4: Encoding and encryption of inputs
# For correct CKKS decryption, the messages have to be much smaller than the FHEW plaintext modulus!
# Inputs
x1 = [1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0]
x2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
x1Rot = RotateInt(x1,1)
x1Rot = [x1Rot[i] + x1[i] for i in range(len(x1))]
x1Int = [int(round(0.25 * elem * elem) % pLWE1) for elem in x1Rot]
x2Rot = RotateInt(x2,2)
x2Rot = [x2Rot[i] + x2[i] for i in range(len(x2))]
x2Int = [int(round(0.25 * elem * elem) % pLWE2) for elem in x2Rot]
# Encrypt
# encrypted under small plantext modulus p = 4 and ciphertext modulus
ctxtsLWE1 = [ccLWE.Encrypt(privateKeyFHEW, x1[i]) for i in range(slots)]
# encrypted under large plaintext modulus and large ciphertext modulus
ctxtsLWE2 = [ccLWE.Encrypt(privateKeyFHEW, x2[i], FRESH, pLWE2, modulus_LWE) for i in range(slots)]
# Step 5. Perform the scheme switching
cTemp = cc.EvalFHEWtoCKKS(ctxtsLWE1, slots, slots)
print(f"\n---Input x1: {x1} encrypted under p = 4 and Q = {ctxtsLWE1[0].GetModulus()} ---\n")
print(f"round( 0.5 * (x1 + rot(x1,1) )^2 ): {x1Int}\n")
# Step 6. Perform the desired computation in CKKS
cPoly = cc.EvalAdd(cTemp, cc.EvalRotate(cTemp, 1))
cPoly = cc.EvalMult(cc.EvalMult(cPoly, cPoly), 0.25)
# Perform the precomputation for switching back to CKKS
cc.EvalCKKStoFHEWPrecompute(scale1)
# Tranform the ciphertext from CKKS to FHEW
cTemp1 = cc.EvalCKKStoFHEW(cPoly, slots)
print(f"\nFHEW decryption with plaintext modulus {pLWE1}: ", end="")
for i in range(len(cTemp1)):
result = ccLWE.Decrypt(privateKeyFHEW, cTemp1[i], pLWE1)
print(result, end=" ")
print("\n")
# Step 5'. Perform the scheme switching
cTemp = cc.EvalFHEWtoCKKS(ctxtsLWE2, slots, slots, pLWE2, 0, pLWE2)
print(f"\n---Input x2: {x2} encrypted under p = {pLWE2} and Q = {ctxtsLWE2[0].GetModulus()} ---\n")
print(f"round( 0.5 * (x2 + rot(x2,2) )^2 ): {x2Int}\n")
# Step 6'. Perform the desired computation in CKKS
cPoly = cc.EvalAdd(cTemp, cc.EvalRotate(cTemp, 2))
cPoly = cc.EvalMult(cc.EvalMult(cPoly, cPoly), 0.25)
# Perform the precomputation for switching back to CKKS
cc.EvalCKKStoFHEWPrecompute(scale2)
# Tranform the ciphertext from CKKS to FHEW
cTemp2 = cc.EvalCKKStoFHEW(cPoly, slots)
print(f"\nFHEW decryption with plaintext modulus {pLWE2}: ", end="")
for i in range(len(cTemp2)):
result = ccLWE.Decrypt(privateKeyFHEW, cTemp2[i], pLWE2)
print(result, end=" ")
print("\n")
def ComparisonViaSchemeSwitching():
print("\n-----ComparisonViaSchemeSwitching-----\n")
print("Output precision is only wrt the operations in CKKS after switching back.\n")
# Step 1: Setup CryptoContext for CKKS
scTech = FIXEDAUTO
multDepth = 17
if scTech == FLEXIBLEAUTOEXT:
multDepth += 1
scaleModSize = 50
firstModSize = 60
ringDim = 8192
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 25
slots = 16 # sparsely-packed
batchSize = slots
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetScalingModSize(scaleModSize)
parameters.SetFirstModSize(firstModSize)
parameters.SetScalingTechnique(scTech)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
parameters.SetSecretKeyDist(UNIFORM_TERNARY)
parameters.SetKeySwitchTechnique(HYBRID)
parameters.SetNumLargeDigits(3)
cc = GenCryptoContext(parameters)
# Enable the features that you wish to use
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(ADVANCEDSHE)
cc.Enable(SCHEMESWITCH)
print(f"CKKS scheme is using ring dimension {cc.GetRingDimension()},\n and number of slots {slots}\n and supports a multiplicative depth of {multDepth}\n")
# Generate encryption keys.
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
params = SchSwchParams()
params.SetSecurityLevelCKKS(sl)
params.SetSecurityLevelFHEW(slBin)
params.SetCtxtModSizeFHEWLargePrec(logQ_ccLWE)
params.SetNumSlotsCKKS(slots)
params.SetNumValues(slots)
privateKeyFHEW = cc.EvalSchemeSwitchingSetup(params)
ccLWE = cc.GetBinCCForSchemeSwitch()
cc.EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW)
print(f"FHEW scheme is using lattice parameter {ccLWE.Getn()},\n logQ {logQ_ccLWE},\n and modulus q {ccLWE.Getq()}\n")
# Set the scaling factor to be able to decrypt; the LWE mod switch is performed on the ciphertext at the last level
pLWE1 = ccLWE.GetMaxPlaintextSpace() # Small precision
modulus_LWE = 1 << logQ_ccLWE
beta = ccLWE.GetBeta()
pLWE2 = int(modulus_LWE / (2 * beta)) # Large precision
scaleSignFHEW = 1.0
cc.EvalCompareSwitchPrecompute(pLWE2, scaleSignFHEW)
# Step 3: Encoding and encryption of inputs
x1 = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0]
x2 = [5.25] * slots
ptxt1 = cc.MakeCKKSPackedPlaintext(x1, 1, 0, None, slots)
ptxt2 = cc.MakeCKKSPackedPlaintext(x2, 1, 0, None, slots)
c1 = cc.Encrypt(keys.publicKey, ptxt1)
c2 = cc.Encrypt(keys.publicKey, ptxt2)
cDiff = cc.EvalSub(c1, c2)
# Step 4: CKKS to FHEW switching and sign evaluation to test correctness
pDiff = cc.Decrypt(keys.secretKey, cDiff)
pDiff.SetLength(slots)
print("Difference of inputs: ", end="")
for i in range(slots):
print(pDiff.GetRealPackedValue()[i], end=" ")
eps = 0.0001
print("\nExpected sign result from CKKS: ", end="")
for i in range(slots):
print(int(round(pDiff.GetRealPackedValue()[i] / eps) * eps < 0), end=" ")
print()
LWECiphertexts = cc.EvalCKKStoFHEW(cDiff, slots)
print("\nFHEW decryption with plaintext modulus ", pLWE2, ": ", end="")
for i in range(len(LWECiphertexts)):
plainLWE = ccLWE.Decrypt(privateKeyFHEW, LWECiphertexts[i], pLWE2)
print(plainLWE, end=" ")
print("\nExpected sign result in FHEW with plaintext modulus ", pLWE2, " and scale ", scaleSignFHEW, ": ", end="")
for i in range(slots):
print((int(round(pDiff.GetRealPackedValue()[i] * scaleSignFHEW)) % pLWE2 - pLWE2 / 2.0 >= 0), end=" ")
print()
print("Obtained sign result in FHEW with plaintext modulus ", pLWE2, " and scale ", scaleSignFHEW, ": ", end="")
LWESign = [None] * len(LWECiphertexts)
for i in range(len(LWECiphertexts)):
LWESign[i] = ccLWE.EvalSign(LWECiphertexts[i])
plainLWE = ccLWE.Decrypt(privateKeyFHEW, LWESign[i], 2)
print(plainLWE, end=" ")
print()
# Step 5'': Direct comparison via CKKS->FHEW->CKKS
cResult = cc.EvalCompareSchemeSwitching(c1, c2, slots, slots)
plaintextDec3 = cc.Decrypt(keys.secretKey, cResult)
plaintextDec3.SetLength(slots)
print(f"Decrypted switched result: {plaintextDec3}\n")
def ArgminViaSchemeSwitching():
print("\n-----ArgminViaSchemeSwitching-----\n")
print("Output precision is only wrt the operations in CKKS after switching back\n")
# Step 1: Setup CryptoContext for CKKS
scaleModSize = 50
firstModSize = 60
ringDim = 8192
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 25
arbFunc = False
oneHot = True # Change to false if the output should not be one-hot encoded
slots = 16 # sparsely-packed
batchSize = slots
numValues = 16
scTech = FIXEDMANUAL
multDepth = 9 + 3 + 1 + int(log2(numValues)) # 13 for FHEW to CKKS, log2(numValues) for argmin
if scTech == FLEXIBLEAUTOEXT:
multDepth += 1
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetScalingModSize(scaleModSize)
parameters.SetFirstModSize(firstModSize)
parameters.SetScalingTechnique(scTech)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
cc = GenCryptoContext(parameters)
# Enable the features that you wish to use
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(ADVANCEDSHE)
cc.Enable(SCHEMESWITCH)
print("CKKS scheme is using ring dimension ", cc.GetRingDimension())
print(", and number of slots ", slots, ", and supports a depth of ", multDepth, "\n")
# Generate encryption keys
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
params = SchSwchParams()
params.SetSecurityLevelCKKS(sl)
params.SetSecurityLevelFHEW(slBin)
params.SetCtxtModSizeFHEWLargePrec(logQ_ccLWE)
params.SetNumSlotsCKKS(slots)
params.SetNumValues(numValues)
params.SetComputeArgmin(True)
privateKeyFHEW = cc.EvalSchemeSwitchingSetup(params)
ccLWE = cc.GetBinCCForSchemeSwitch()
cc.EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW)
print(f"FHEW scheme is using lattice parameter {ccLWE.Getn()},\n logQ {logQ_ccLWE},\n and modulus q {ccLWE.Getq()}\n")
# Scale the inputs to ensure their difference is correctly represented after switching to FHEW
scaleSign = 512
modulus_LWE = 1 << logQ_ccLWE
beta = ccLWE.GetBeta()
pLWE = int(modulus_LWE / (2 * beta)) # Large precision
cc.EvalCompareSwitchPrecompute(pLWE, scaleSign)
# Step 3: Encoding and encryption of inputs
x1 = [-1.125, -1.12, 5.0, 6.0, -1.0, 2.0, 8.0, -1.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.25, 15.30]
print("Expected minimum value ", min(x1), " at location ", x1.index(min(x1)))
print("Expected maximum value ", max(x1), " at location ", x1.index(max(x1)))
ptxt1 = cc.MakeCKKSPackedPlaintext(x1)
c1 = cc.Encrypt(keys.publicKey, ptxt1)
# Step 4: Argmin evaluation
result = cc.EvalMinSchemeSwitching(c1, keys.publicKey, numValues, slots)
ptxtMin = cc.Decrypt(keys.secretKey, result[0])
ptxtMin.SetLength(1)
print("Minimum value: ", ptxtMin)
ptxtMin = cc.Decrypt(keys.secretKey, result[1])
if oneHot:
ptxtMin.SetLength(numValues)
print("Argmin indicator vector: ", ptxtMin)
else:
ptxtMin.SetLength(1)
print("Argmin: ", ptxtMin)
result = cc.EvalMaxSchemeSwitching(c1, keys.publicKey, numValues, slots)
ptxtMax = cc.Decrypt(keys.secretKey, result[0])
ptxtMax.SetLength(1)
print("Maximum value: ", ptxtMax)
ptxtMax = cc.Decrypt(keys.secretKey, result[1])
if oneHot:
ptxtMax.SetLength(numValues)
print("Argmax indicator vector: ", ptxtMax)
else:
ptxtMax.SetLength(1)
print("Argmax: ", ptxtMax)
def ArgminViaSchemeSwitchingAlt():
print("\n-----ArgminViaSchemeSwitchingAlt-----\n")
print("Output precision is only wrt the operations in CKKS after switching back\n")
# Step 1: Setup CryptoContext for CKKS
scaleModSize = 50
firstModSize = 60
ringDim = 8192
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 25
arbFunc = False
oneHot = True
alt = True
slots = 16
batchSize = slots
numValues = 16
scTech = FIXEDAUTO
multDepth = 9 + 3 + 1 + int(log2(numValues))
parameters = CCParamsCKKSRNS()
parameters.SetMultiplicativeDepth(multDepth)
parameters.SetScalingModSize(scaleModSize)
parameters.SetFirstModSize(firstModSize)
parameters.SetScalingTechnique(scTech)
parameters.SetSecurityLevel(sl)
parameters.SetRingDim(ringDim)
parameters.SetBatchSize(batchSize)
cc = GenCryptoContext(parameters)
cc.Enable(PKE)
cc.Enable(KEYSWITCH)
cc.Enable(LEVELEDSHE)
cc.Enable(ADVANCEDSHE)
cc.Enable(SCHEMESWITCH)
print(f"CKKS scheme is using ring dimension {cc.GetRingDimension()},")
print(f"number of slots {slots}, and supports a multiplicative depth of {multDepth}\n")
keys = cc.KeyGen()
# Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
params = SchSwchParams()
params.SetSecurityLevelCKKS(sl)
params.SetSecurityLevelFHEW(slBin)
params.SetCtxtModSizeFHEWLargePrec(logQ_ccLWE)
params.SetNumSlotsCKKS(slots)
params.SetNumValues(numValues)
params.SetComputeArgmin(True)
params.SetUseAltArgmin(True)
privateKeyFHEW = cc.EvalSchemeSwitchingSetup(params)
ccLWE = cc.GetBinCCForSchemeSwitch()
cc.EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW)
print(f"FHEW scheme is using lattice parameter {ccLWE.Getn()},\n logQ {logQ_ccLWE},\n and modulus q {ccLWE.Getq()}\n")
scaleSign = 512
modulus_LWE = 1 << logQ_ccLWE
beta = ccLWE.GetBeta()
pLWE = int(modulus_LWE / (2 * beta))
cc.EvalCompareSwitchPrecompute(pLWE, scaleSign)
# Step 3: Encoding and encryption of inputs
# Inputs
x1 = [-1.125, -1.12, 5.0, 6.0, -1.0, 2.0, 8.0, -1.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.25, 15.30]
print("Expected minimum value ", min(x1), " at location ", x1.index(min(x1)))
print("Expected maximum value ", max(x1), " at location ", x1.index(max(x1)))
# Encoding as plaintexts
ptxt1 = cc.MakeCKKSPackedPlaintext(x1) # Only if we set batchsize
# ptxt1 = cc.MakeCKKSPackedPlaintext(x1, 1, 0, None, slots) # If batchsize is not set
# Encrypt the encoded vectors
c1 = cc.Encrypt(keys.publicKey, ptxt1)
# Step 4: Argmin evaluation
result = cc.EvalMinSchemeSwitchingAlt(c1, keys.publicKey, numValues, slots)
ptxtMin = cc.Decrypt(keys.secretKey, result[0])
ptxtMin.SetLength(1)
print("Minimum value: ", ptxtMin)
ptxtMin = cc.Decrypt(keys.secretKey, result[1])
if oneHot:
ptxtMin.SetLength(numValues)
print("Argmin indicator vector: ", ptxtMin)
else:
ptxtMin.SetLength(1)
print("Argmin: ", ptxtMin)
result = cc.EvalMaxSchemeSwitchingAlt(c1, keys.publicKey, numValues, slots)
ptxtMax = cc.Decrypt(keys.secretKey, result[0])
ptxtMax.SetLength(1)
print("Maximum value: ", ptxtMax)
ptxtMax = cc.Decrypt(keys.secretKey, result[1])
if oneHot:
ptxtMax.SetLength(numValues)
print("Argmax indicator vector: ", ptxtMax)
else:
ptxtMax.SetLength(1)
print("Argmax: ", ptxtMax)
def ArgminViaSchemeSwitchingUnit():
print("\n-----ArgminViaSchemeSwitchingUnit-----\n")
print("Output precision is only wrt the operations in CKKS after switching back\n")
# Step 1: Setup CryptoContext for CKKS
scaleModSize = 50
firstModSize = 60
ringDim = 8192
sl = HEStd_NotSet
slBin = TOY
logQ_ccLWE = 25
arbFunc = False
oneHot = True