yaole
47 lines
1.3 KiB
Go
47 lines
1.3 KiB
Go
package paillier
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import (
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"math/big"
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"xdx.jelly/xgcl/gmath"
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)
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// HomomorphicAdd set c = Enc(m1+m2) where c1 = Enc(m1) and c2 = Enc(m2)
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func (c *Cipher) HomomorphicAdd(c1 *Cipher, c2 *Cipher, pk *PublicKey) *Cipher {
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if c.D == nil {
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c.D = new(big.Int)
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}
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c.D.Mul(c1.D, c2.D)
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c.D.Mod(c.D, pk.N2)
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return c
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}
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// HomomorphicAddInt set c = Enc(m1 + m) where c1 = Enc(m1) and m < N.
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//
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// Becareful, if the adversary knows c1, c, and m(or m1), then he can computes m1(or m).
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// So, using HomomorphicAddInt if you know what you're doing,
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// otherwise, you should use like this:
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// c2, err := pk.Encrypt(m, rnd)
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// c.HomomorphicAdd(c1, c2, pk)
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func (c *Cipher) HomomorphicAddInt(c1 *Cipher, m *big.Int, pk *PublicKey) *Cipher {
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d := new(big.Int)
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c.D = d.Mul(pk.N, m).Add(d, gmath.BigInt1).Mod(d, pk.N2).Mul(d, c1.D).Mod(d, pk.N2)
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return c
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}
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// HomomorphicScalarMul if c1 = Enc(a), then HomomorphicScalarMul computes c = Enc(ka)
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// if ka < n^2.
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func (c *Cipher) HomomorphicScalarMul(a *Cipher, k *big.Int, pk *PublicKey) *Cipher {
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if c.D == nil {
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c.D = new(big.Int)
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}
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c.D.Exp(a.D, k, pk.N2)
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return c
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}
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// Neg negates the plaintext mod n, i.e., if c = Enc(m), then c.Neg() = Enc(n-m).
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func (c *Cipher) Neg(pk *PublicKey) *Cipher {
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c.D.ModInverse(c.D, pk.N2)
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return c
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}
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