Homomorphic ciphertext operations

Focus: a concrete balance update that subtracts a fee, adds a reward, and scales the encrypted amount.

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entry init() {
    let balance = Ciphertext::zero();
    balance.add(100);
    balance.sub(25);
    balance.add(12);
    balance.mul(2);
    println(balance)
 
    require(
        balance.commitment() == Scalar::from_u64(174).mul_base(),
        "Encrypted value should be equal to 174"
    )
    return 0
}
 
entry combine(left: Ciphertext, right: Ciphertext) -> Ciphertext {
    left.add_ct(right);
    return left
}

How it works

• Ciphertext::generate(recipient, amount) creates an encrypted amount for the recipient address, while Ciphertext::zero() creates an encrypted zero value to build up from.
• encrypted.add(value) adds a plaintext amount to the ciphertext in place.
• encrypted.sub(value) subtracts a plaintext amount from the ciphertext in place.
• encrypted.mul(value) scales the ciphertext by a plaintext multiplier.
• The resulting ciphertext is equal to ((100 - 25 + 12) * 2) and can be applied to others ciphertexts.