Created
September 3, 2019 16:56
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/*N is signal size (number of samples), sampleRate in kHz (num samples per ms), frameLength in ms, shiftLength in ms*/ | |
vector<vector<Ciphertext<DCRTPoly>>> real_discrete_fourier_transform(int N, int sampleRate, int frameLength, int shiftLength, CryptoContext<DCRTPoly> cc, LPPublicKey<DCRTPoly> publicKey, CryptoFractions encSignal, LPPrivateKey<DCRTPoly> sk) { | |
int boundN, boundM; | |
if (N % 2 == 0) { | |
boundM = N / 2 - 1; | |
boundN = N / 2; | |
} | |
else { | |
boundM = (N - 1) / 2; | |
boundN = (N - 1) / 2; | |
} | |
vector<int64_t> zeros = { 0 }; | |
vector<int64_t> one = { 1 }; | |
for (int i = 0; i < frameLength - 1; i += 1) { | |
zeros.push_back(0); | |
one.push_back(0); | |
} | |
Plaintext zerosPT1 = cc->MakePackedPlaintext(zeros); | |
Plaintext zerosPT2 = cc->MakePackedPlaintext(zeros); | |
Plaintext onePTRe = cc->MakePackedPlaintext(one); | |
Plaintext onePTIm = cc->MakePackedPlaintext(one); | |
Ciphertext<DCRTPoly> zerosCT1; | |
Ciphertext<DCRTPoly> zerosCT2; | |
Ciphertext<DCRTPoly> oneCTRe; | |
Ciphertext<DCRTPoly> oneCTIm; | |
zerosCT1 = cc->Encrypt(publicKey, zerosPT1); | |
zerosCT2 = cc->Encrypt(publicKey, zerosPT2); | |
oneCTRe = cc->Encrypt(publicKey, onePTRe); | |
oneCTIm = cc->Encrypt(publicKey, onePTIm); | |
int numSamplesInFrame = sampleRate * frameLength; | |
int numSamplesInShift = sampleRate * shiftLength; | |
unsigned long batchSize = upper_power_of_two(numSamplesInFrame); | |
Plaintext cosines; | |
Plaintext sines; | |
Ciphertext<DCRTPoly> innerProductRe; | |
Ciphertext<DCRTPoly> innerProductIm; | |
Ciphertext<DCRTPoly> resultRe; | |
Ciphertext<DCRTPoly> resultReSquared; | |
Ciphertext<DCRTPoly> resultIm; | |
Ciphertext<DCRTPoly> resultImSquared; | |
Ciphertext<DCRTPoly> resultRDFT; | |
vector<vector<Ciphertext<DCRTPoly>>> resultsRe = vector<vector<Ciphertext<DCRTPoly>>>(int(ceil(float(N) / float(numSamplesInShift)))); | |
vector<vector<Ciphertext<DCRTPoly>>> resultsIm = vector<vector<Ciphertext<DCRTPoly>>>(int(ceil(float(N) / float(numSamplesInShift)))); | |
vector<vector<Ciphertext<DCRTPoly>>> RDFT = vector<vector<Ciphertext<DCRTPoly>>>(int(ceil(float(N) / float(numSamplesInShift)))); | |
int atFrame = 0; | |
resultsIm[atFrame].push_back(zerosCT1); | |
for (int i = 0; i <= N; i += numSamplesInShift) { | |
for (int n = 0; n <= boundN; n++) { | |
cosines = calculate_cosines(boundN, n, N, i, i + numSamplesInFrame, cc, publicKey); | |
innerProductRe = cc->EvalInnerProduct(encSignal.encryptedNumerators, cosines, batchSize); | |
resultRe = cc->EvalMult(innerProductRe, oneCTRe); | |
resultsRe[atFrame].push_back(resultRe); | |
resultReSquared = cc->EvalMult(resultRe, resultRe); | |
if ((n + 1) <= boundM) { | |
sines = calculate_sines(boundM, n + 1, N, i, i + numSamplesInFrame, cc, publicKey); | |
innerProductIm = cc->EvalInnerProduct(encSignal.encryptedNumerators, sines, batchSize); | |
resultIm = cc->EvalMult(innerProductIm, oneCTIm); | |
resultsIm[atFrame].push_back(resultIm); | |
resultImSquared = cc->EvalMult(resultIm, resultIm); | |
} | |
else if ((n + 1) == boundM+1) { | |
resultsIm[atFrame].push_back(zerosCT2); | |
} | |
Plaintext result; | |
resultRDFT = cc->EvalAdd(resultReSquared, resultImSquared); | |
RDFT[atFrame].push_back(resultRDFT); | |
} | |
atFrame += 1; | |
} | |
return RDFT; | |
} |
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