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mp-spdz-rs: fhe: Add Ciphertext and keypair bindings + arithmetic
This provides a high level interface over the the BGV implementation in MP-SPDZ that avoids calling directly into the ffi.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,200 @@ | ||
| //! Ciphertext wrapper around the MP-SPDZ `Ciphertext` struct | ||
| use std::{ | ||
| marker::PhantomData, | ||
| ops::{Add, Mul}, | ||
| }; | ||
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| use ark_ec::CurveGroup; | ||
| use cxx::UniquePtr; | ||
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| use crate::ffi::{ | ||
| add_ciphertexts as ffi_add_cipher, add_plaintext as ffi_add_plaintext, | ||
| mul_ciphertexts as ffi_mul_ciphertext, mul_plaintext as ffi_mul_plaintext, | ||
| Ciphertext as FfiCiphertext, | ||
| }; | ||
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| use super::{keys::BGVPublicKey, plaintext::Plaintext}; | ||
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| /// A ciphertext in the BGV implementation | ||
| /// | ||
| /// The ciphertext is defined over the Scalar field of the curve group | ||
| pub struct Ciphertext<C: CurveGroup> { | ||
| /// The wrapped MP-SPDZ `Ciphertext` | ||
| pub(crate) inner: UniquePtr<FfiCiphertext>, | ||
| /// Phantom | ||
| _phantom: PhantomData<C>, | ||
| } | ||
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| impl<C: CurveGroup> Ciphertext<C> { | ||
| /// Multiply two ciphertexts | ||
| pub fn mul_ciphertext(&self, other: &Self, pk: &BGVPublicKey<C>) -> Self { | ||
| ffi_mul_ciphertext(self.as_ref(), other.as_ref(), pk.as_ref()).into() | ||
| } | ||
| } | ||
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| impl<C: CurveGroup> From<UniquePtr<FfiCiphertext>> for Ciphertext<C> { | ||
| fn from(inner: UniquePtr<FfiCiphertext>) -> Self { | ||
| Self { inner, _phantom: PhantomData } | ||
| } | ||
| } | ||
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| impl<C: CurveGroup> AsRef<FfiCiphertext> for Ciphertext<C> { | ||
| fn as_ref(&self) -> &FfiCiphertext { | ||
| self.inner.as_ref().unwrap() | ||
| } | ||
| } | ||
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| impl<C: CurveGroup> Add<&Plaintext<C>> for &Ciphertext<C> { | ||
| type Output = Ciphertext<C>; | ||
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| fn add(self, rhs: &Plaintext<C>) -> Self::Output { | ||
| ffi_add_plaintext(self.as_ref(), rhs.as_ref()).into() | ||
| } | ||
| } | ||
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| impl<C: CurveGroup> Add for &Ciphertext<C> { | ||
| type Output = Ciphertext<C>; | ||
|
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| fn add(self, rhs: Self) -> Self::Output { | ||
| ffi_add_cipher(self.as_ref(), rhs.as_ref()).into() | ||
| } | ||
| } | ||
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| impl<C: CurveGroup> Mul<&Plaintext<C>> for &Ciphertext<C> { | ||
| type Output = Ciphertext<C>; | ||
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| fn mul(self, rhs: &Plaintext<C>) -> Self::Output { | ||
| ffi_mul_plaintext(self.as_ref(), rhs.as_ref()).into() | ||
| } | ||
| } | ||
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| #[cfg(test)] | ||
| mod test { | ||
| use rand::{thread_rng, Rng, RngCore}; | ||
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| use crate::fhe::{keys::BGVKeypair, params::BGVParams, plaintext::Plaintext}; | ||
| use crate::TestCurve; | ||
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| use super::Ciphertext; | ||
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| /// Setup the FHE scheme | ||
| fn setup_fhe() -> (BGVParams<TestCurve>, BGVKeypair<TestCurve>) { | ||
| let params = BGVParams::new(1 /* n_mults */); | ||
| let keypair = BGVKeypair::gen(¶ms); | ||
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| (params, keypair) | ||
| } | ||
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| /// Get a plaintext with the given value in the first slot | ||
| fn plaintext_int(val: u32, params: &BGVParams<TestCurve>) -> Plaintext<TestCurve> { | ||
| let mut plaintext = Plaintext::new(params); | ||
| plaintext.set_element(0, val); | ||
|
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| plaintext | ||
| } | ||
|
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| /// Get the ciphertext with the given value in the first slot | ||
| fn encrypt_int( | ||
| value: u32, | ||
| keypair: &BGVKeypair<TestCurve>, | ||
| params: &BGVParams<TestCurve>, | ||
| ) -> Ciphertext<TestCurve> { | ||
| let plaintext = plaintext_int(value, params); | ||
| keypair.encrypt(&plaintext) | ||
| } | ||
|
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| /// Tests addition of a ciphertext with a plaintext | ||
| #[test] | ||
| fn test_ciphertext_plaintext_addition() { | ||
| let mut rng = thread_rng(); | ||
| let (params, mut keypair) = setup_fhe(); | ||
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| // Add a ciphertext with a plaintext | ||
| let val1 = rng.next_u32() / 2; | ||
| let val2 = rng.next_u32() / 2; | ||
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| let plaintext = plaintext_int(val2, ¶ms); | ||
| let ciphertext = encrypt_int(val1, &keypair, ¶ms); | ||
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| let sum = &ciphertext + &plaintext; | ||
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| // Decrypt the sum | ||
| let plaintext_res = keypair.decrypt(&sum); | ||
| let res = plaintext_res.get_element(0); | ||
| let expected = val1 + val2; | ||
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| assert_eq!(res, expected); | ||
| } | ||
|
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| /// Tests multiplication of a ciphertext with a plaintext | ||
| #[test] | ||
| fn test_ciphertext_plaintext_multiplication() { | ||
| let mut rng = thread_rng(); | ||
| let (params, mut keypair) = setup_fhe(); | ||
|
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| // Multiply a ciphertext with a plaintext | ||
| let range = 0..(1u32 << 16); | ||
| let val1 = rng.gen_range(range.clone()); | ||
| let val2 = rng.gen_range(range); | ||
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| let plaintext = plaintext_int(val2, ¶ms); | ||
| let ciphertext = encrypt_int(val1, &keypair, ¶ms); | ||
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| let product = &ciphertext * &plaintext; | ||
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| // Decrypt the product | ||
| let plaintext_res = keypair.decrypt(&product); | ||
| let res = plaintext_res.get_element(0); | ||
| let expected = val1 * val2; | ||
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| assert_eq!(res, expected); | ||
| } | ||
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| /// Tests addition of two ciphertexts | ||
| #[test] | ||
| fn test_ciphertext_ciphertext_addition() { | ||
| let mut rng = thread_rng(); | ||
| let (params, mut keypair) = setup_fhe(); | ||
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| // Add two ciphertexts | ||
| let val1 = rng.next_u32() / 2; | ||
| let val2 = rng.next_u32() / 2; | ||
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| let ciphertext1 = encrypt_int(val1, &keypair, ¶ms); | ||
| let ciphertext2 = encrypt_int(val2, &keypair, ¶ms); | ||
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| let sum = &ciphertext1 + &ciphertext2; | ||
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| // Decrypt the sum | ||
| let plaintext_res = keypair.decrypt(&sum); | ||
| let res = plaintext_res.get_element(0); | ||
| let expected = val1 + val2; | ||
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| assert_eq!(res, expected); | ||
| } | ||
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| /// Tests multiplication of two ciphertexts | ||
| #[test] | ||
| fn test_ciphertext_ciphertext_multiplication() { | ||
| let mut rng = thread_rng(); | ||
| let (params, mut keypair) = setup_fhe(); | ||
|
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| // Multiply two ciphertexts | ||
| let range = 0..(1u32 << 16); | ||
| let val1 = rng.gen_range(range.clone()); | ||
| let val2 = rng.gen_range(range); | ||
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| let ciphertext1 = encrypt_int(val1, &keypair, ¶ms); | ||
| let ciphertext2 = encrypt_int(val2, &keypair, ¶ms); | ||
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| let product = ciphertext1.mul_ciphertext(&ciphertext2, &keypair.public_key); | ||
|
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| // Decrypt the product | ||
| let plaintext_res = keypair.decrypt(&product); | ||
| let res = plaintext_res.get_element(0); | ||
| let expected = val1 * val2; | ||
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| assert_eq!(res, expected); | ||
| } | ||
| } |
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