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Classical Fully Homomorphic Encryption for Quantum Circuits: Difference between revisions
Classical Fully Homomorphic Encryption for Quantum Circuits (edit)
Revision as of 00:02, 26 November 2018
, 26 November 2018→Stage 2 Server’s Computation
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### if <math>c_i=</math>P then <div class="floatright">//Pauli Gate</div></br><math>(\tilde {x}^{[l]},\tilde{z}^{[l]})\rightarrow (\tilde{x}^{[l]},\tilde{x}^{[l]}\oplus\tilde{z}^{[l]})</math> | ### if <math>c_i=</math>P then <div class="floatright">//Pauli Gate</div></br><math>(\tilde {x}^{[l]},\tilde{z}^{[l]})\rightarrow (\tilde{x}^{[l]},\tilde{x}^{[l]}\oplus\tilde{z}^{[l]})</math> | ||
### if <math>c_i=CNOT_{l,n}</math> with m as target bit and n as control bit then <div class="floatright">//CNOT</div></br>(<math>\tilde {x}^{[l]},\tilde{z}^{[l]};\tilde {x}^{[n]},\tilde{z}^{[n]})\rightarrow (\tilde {x}^{[l]},\tilde{z}^{[l]}\oplus \tilde {z}^{[n]};\tilde{x}^{[l]}\oplus \tilde {x}^{[n]},\tilde{z}^{[n]})</math> | ### if <math>c_i=CNOT_{l,n}</math> with m as target bit and n as control bit then <div class="floatright">//CNOT</div></br>(<math>\tilde {x}^{[l]},\tilde{z}^{[l]};\tilde {x}^{[n]},\tilde{z}^{[n]})\rightarrow (\tilde {x}^{[l]},\tilde{z}^{[l]}\oplus \tilde {z}^{[n]};\tilde{x}^{[l]}\oplus \tilde {x}^{[n]},\tilde{z}^{[n]})</math> | ||
## If <math>c_i=T</math> gate then <div class="floatright">//Toffoli Gate on <math>l_{th}, n_{th}, o_{th}</math> key bits</div></br> The Toffoli gate application can be deduced as follows:</br><math>TZ^{z^{[l]}}X^{x^{[l]}}Z^{z^{[n]}}X^{x^{[n]}}Z^{z^{[o]}}X^{x^{[o]}}|\psi\rangle</math></br><math>=TZ^{z^{[l]}}X^{x^{[l]}}Z^{z^{[n]}}X^{x^{[n]}}Z^{z^{[o]}}X^{x^{[o]}}T\dagger T|\psi\rangle</math></br><math>=CNOT_{l,o}^{x^{[n]}}CNOT_{n,o}^{x^{[l]}}CZ_{l,n}^{z^{[o]}}Z^{z^{[l]}}X^{x^{[l]}}T|\psi\rangle</math></br><math>=CNOT_{l,o}^{x^{[n]}}CNOT_{n,o}^{x^{[l]}}H_nCNOT_{l,n}^{z^{[o]}}H_{n}Z^{z^{[l]}}X^{x^{[l]}}T|\psi\rangle</math></br><math>=C_{zx}P_{zx}T|\psi\rangle</math>, where <math>C\epsilon \{\text{CNOT,H}\}</math> and <math>P\epsilon\{X,Z\}</math> | ## If <math>c_i=T</math> gate then <div class="floatright">//Toffoli Gate on <math>l_{th}, n_{th}, o_{th}</math> key bits</div></br> <div style="background-color: white; border: solid thin black;title=Functionality Description;"> | ||
The Toffoli gate application can be deduced as follows:</br><math>TZ^{z^{[l]}}X^{x^{[l]}}Z^{z^{[n]}}X^{x^{[n]}}Z^{z^{[o]}}X^{x^{[o]}}|\psi\rangle</math></br><math>=TZ^{z^{[l]}}X^{x^{[l]}}Z^{z^{[n]}}X^{x^{[n]}}Z^{z^{[o]}}X^{x^{[o]}}T\dagger T|\psi\rangle</math></br><math>=CNOT_{l,o}^{x^{[n]}}CNOT_{n,o}^{x^{[l]}}CZ_{l,n}^{z^{[o]}}Z^{z^{[l]}}X^{x^{[l]}}T|\psi\rangle</math></br><math>=CNOT_{l,o}^{x^{[n]}}CNOT_{n,o}^{x^{[l]}}H_nCNOT_{l,n}^{z^{[o]}}H_{n}Z^{z^{[l]}}X^{x^{[l]}}T|\psi\rangle</math></br><math>=C_{zx}P_{zx}T|\psi\rangle</math>, where <math>C\epsilon \{\text{CNOT,H}\}</math> and <math>P\epsilon\{X,Z\}</math></div> | |||
###The Pauli key encryptions are homomorphically updated according to <math>P_{zx}</math>.</br> (<math>\tilde {x}^{[l]},\tilde{z}^{[l]};\tilde {x}^{[n]},\tilde{z}^{[n]};\tilde {x}^{[o]},\tilde{z}^{[o]})\rightarrow (\tilde {x}^{[l]},\tilde{z}^{[l]};0,0;0,0)</math> | ###The Pauli key encryptions are homomorphically updated according to <math>P_{zx}</math>.</br> (<math>\tilde {x}^{[l]},\tilde{z}^{[l]};\tilde {x}^{[n]},\tilde{z}^{[n]};\tilde {x}^{[o]},\tilde{z}^{[o]})\rightarrow (\tilde {x}^{[l]},\tilde{z}^{[l]};0,0;0,0)</math> | ||
### Three encrypted CNOTs are used to correct <math>C^{zx}</math> as follows under <math>\mathrm{AltHE}</math>. | ### Three encrypted CNOTs are used to correct <math>C^{zx}</math> as follows under <math>\mathrm{AltHE}</math>. | ||
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####Server measures the last register to get <math>y =\mathrm{AltHE.Enc}(\mu_0,r_0)=\mathrm{AltHE.Enc}_{pk}(\mu_1,r_1)\oplus_H AltHE.Enc_{pk}(s)</math>.</br> The resulting superposition state is:<math>\sum_{a,b,\mu\in\{0,1\},r}\alpha_{ab}\sqrt{D(\mu_0,r_0)}|a,b\rangle|\mu_a,r_a\rangle|\mathrm{AltHE.Enc}(\mu_0,r_0)\rangle=\sum_{a,b,\mu\in\{0,1\},r}\alpha_{ab}\sqrt{D(\mu_0,r_0)}|a,b\rangle|\mu_a,r_a\rangle|y\rangle</math> | ####Server measures the last register to get <math>y =\mathrm{AltHE.Enc}(\mu_0,r_0)=\mathrm{AltHE.Enc}_{pk}(\mu_1,r_1)\oplus_H AltHE.Enc_{pk}(s)</math>.</br> The resulting superposition state is:<math>\sum_{a,b,\mu\in\{0,1\},r}\alpha_{ab}\sqrt{D(\mu_0,r_0)}|a,b\rangle|\mu_a,r_a\rangle|\mathrm{AltHE.Enc}(\mu_0,r_0)\rangle=\sum_{a,b,\mu\in\{0,1\},r}\alpha_{ab}\sqrt{D(\mu_0,r_0)}|a,b\rangle|\mu_a,r_a\rangle|y\rangle</math> | ||
***'''Encrypted CNOT operation:''' | ***'''Encrypted CNOT operation:''' | ||
<div style="background-color: white; border: solid thin black;title=Functionality Description;"> | |||
<math>\sum_{a,b\in\{0,1\}}\alpha_{ab}CNOT_{a,b}^s|a,b\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}|a,b\oplus a\cdot s\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}|a,b\oplus a\cdot(\mu_0\oplus\mu_1)\rangle</math></br><math>=\sum_{b\in\{0,1\}}\alpha_{0b}|0,b\oplus \mu_0\oplus\mu_0\rangle+\alpha_{1b}|1,b\oplus \mu_0\oplus\mu_1\rangle</math>, <math>\because q\oplus q=0</math></br><math>=\sum_{b\in\{0,1\}}\alpha_{0b}|0\rangle\otimes X^{\mu_0}|b\oplus \mu_0\rangle+\alpha_{1b}|1\rangle \otimes X^{\mu_0}|b\oplus \mu_1\rangle</math>, <math>\because |q\oplus y\rangle=X^y|q\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}|a\rangle\otimes X^{\mu_0}|b\oplus \mu_a\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}(I\otimes X^{\mu_0})|a,b\oplus \mu_a\rangle</math></br> | <math>\sum_{a,b\in\{0,1\}}\alpha_{ab}CNOT_{a,b}^s|a,b\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}|a,b\oplus a\cdot s\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}|a,b\oplus a\cdot(\mu_0\oplus\mu_1)\rangle</math></br><math>=\sum_{b\in\{0,1\}}\alpha_{0b}|0,b\oplus \mu_0\oplus\mu_0\rangle+\alpha_{1b}|1,b\oplus \mu_0\oplus\mu_1\rangle</math>, <math>\because q\oplus q=0</math></br><math>=\sum_{b\in\{0,1\}}\alpha_{0b}|0\rangle\otimes X^{\mu_0}|b\oplus \mu_0\rangle+\alpha_{1b}|1\rangle \otimes X^{\mu_0}|b\oplus \mu_1\rangle</math>, <math>\because |q\oplus y\rangle=X^y|q\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}|a\rangle\otimes X^{\mu_0}|b\oplus \mu_a\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}(I\otimes X^{\mu_0})|a,b\oplus \mu_a\rangle</math></br> | ||
</div> | |||
####Server XORs the second qubit of first register with <math>\mu_a</math> to get:</br><math>\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{a,b}^s|a,b\rangle\otimes|\mu_a,r_a\rangle|y\rangle</math> | ####Server XORs the second qubit of first register with <math>\mu_a</math> to get:</br><math>\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{a,b}^s|a,b\rangle\otimes|\mu_a,r_a\rangle|y\rangle</math> | ||
####Server performs Hadamard on second register. The resulting superposition state is:</br><math>\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{ab}^s|a,b\rangle\otimes H^k|\mu_a,r_a\rangle|y\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{ab}^s|a,b\rangle\otimes\bigg(\sum_{e\in\{0,1\}^k}(-1)^{e\cdot(\mu_a,r_a) }|e\rangle\bigg)|y\rangle</math>, <math>\because H^k|q\rangle=\sum_{e\in\{0,1\}^k}(-1)^{e\cdot q}|e\rangle</math>, where q has k qubits</br> | ####Server performs Hadamard on second register. The resulting superposition state is:</br><math>\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{ab}^s|a,b\rangle\otimes H^k|\mu_a,r_a\rangle|y\rangle</math></br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{ab}^s|a,b\rangle\otimes\bigg(\sum_{e\in\{0,1\}^k}(-1)^{e\cdot(\mu_a,r_a) }|e\rangle\bigg)|y\rangle</math>, <math>\because H^k|q\rangle=\sum_{e\in\{0,1\}^k}(-1)^{e\cdot q}|e\rangle</math>, where q has k qubits</br> | ||
####Server measures the second register to get d. The resulting superposition is:</br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{ab}^s|a,b\rangle\otimes(-1)^{d\cdot(\mu_a,r_a)}|d\rangle|y\rangle</math></br>The first register could be equivalently written as:</br><math>(-1)^{d\cdot(\mu_0,r_0)}|0,b\rangle+(-1)^{d\cdot(\mu_1,r_1)}|1,b\rangle</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}((-1)^{d\cdot((\mu_0,r_0)\oplus(\mu_0,r_0))}|0,b\rangle+(-1)^{d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))}|1,b\rangle)</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}((-1)^{0\cdot(d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))})|0,b\rangle+(-1)^{1\cdot(d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1)))}|1,b\rangle)</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}((-1)^{a\cdot(d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))})|a,b\rangle</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}(Z^{d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))}|a,b\rangle)</math>, <math>\because Z|q\rangle=(-1)^q|q\rangle</math></br>Thus, the resulting state (upto a global phase) is: </br><math>\approx(Z^{d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))}\otimes X^{\mu_0})CNOT_{12}^s\sum_{a,b\in\{0,1\}}\alpha_{ab}|a,b\rangle</math></br><math> | ####Server measures the second register to get d. The resulting superposition is:</br><math>=\sum_{a,b\in\{0,1\}}\alpha_{ab}\sqrt{D(\mu_0,r_0)}(I\otimes X^{\mu_0})CNOT_{ab}^s|a,b\rangle\otimes(-1)^{d\cdot(\mu_a,r_a)}|d\rangle|y\rangle</math></br> | ||
<div style="background-color: white; border: solid thin black;title=Functionality Description;"> | |||
The first register could be equivalently written as:</br><math>(-1)^{d\cdot(\mu_0,r_0)}|0,b\rangle+(-1)^{d\cdot(\mu_1,r_1)}|1,b\rangle</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}((-1)^{d\cdot((\mu_0,r_0)\oplus(\mu_0,r_0))}|0,b\rangle+(-1)^{d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))}|1,b\rangle)</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}((-1)^{0\cdot(d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))})|0,b\rangle+(-1)^{1\cdot(d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1)))}|1,b\rangle)</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}((-1)^{a\cdot(d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))})|a,b\rangle</math></br><math>=(-1)^{d\cdot (\mu_0,r_0)}(Z^{d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))}|a,b\rangle)</math>, <math>\because Z|q\rangle=(-1)^q|q\rangle</math></br>Thus, the resulting state (upto a global phase) is: </br><math>\approx(Z^{d\cdot((\mu_0,r_0)\oplus(\mu_1,r_1))}\otimes X^{\mu_0})CNOT_{12}^s\sum_{a,b\in\{0,1\}}\alpha_{ab}|a,b\rangle</math><div style="background-color: white; border: solid thin black;title=Functionality Description;"></br>Final superposition at the end of encrypted CNOT operation is:</br> <math>(Z^{d\cdot ((\mu_0,r_0)\oplus (\mu_1,r_1))}\otimes X^{\mu_0})\mathrm{CNOT}_{1,2}^s|\psi_{12}\rangle</math> </br>where <math>(\mu_0,r_0)=(\mu_1,r_1)\oplus_H s</math>, as <math>\oplus_H</math> is the homomorphic XOR operation. | |||
####The server uses <math>pk_{i+1}</math> to compute HE.Enc<math>_{pk_{i+1}}(c_{x,z,pk_i})</math> and <math>\mathrm{HE.Enc}_{pk_{i+1}}(\hat{c},y,d)</math>. | ####The server uses <math>pk_{i+1}</math> to compute HE.Enc<math>_{pk_{i+1}}(c_{x,z,pk_i})</math> and <math>\mathrm{HE.Enc}_{pk_{i+1}}(\hat{c},y,d)</math>. | ||
####The server computes the encryption of <math>x,z</math> under <math>pk_{i+1}</math> by homomorphically running the decryption circuit on inputs <math>\mathrm{HE.Enc}_{pk_{i+1}}(sk_i)</math> and <math>\mathrm{HE.Enc}_{pk_{i+1}}(c_{x,z,pk_i})</math>. | ####The server computes the encryption of <math>x,z</math> under <math>pk_{i+1}</math> by homomorphically running the decryption circuit on inputs <math>\mathrm{HE.Enc}_{pk_{i+1}}(sk_i)</math> and <math>\mathrm{HE.Enc}_{pk_{i+1}}(c_{x,z,pk_i})</math>. | ||