4.3.1 Homomorphic Encryption

Flowchart:

Figure 4. Homomorphic Encryption Flowchart

Code example:

from seal import EncryptionParameters, SEALContext, KeyGenerator, Encryptor, Decryptor, Plaintext, Ciphertext

# Set homomorphic encryption parameters
params = EncryptionParameters()
params.set_poly_modulus("1x^4096 + 1")
params.set_coeff_modulus(seal.coeff_modulus_128(4096))
params.set_plain_modulus(1 << 8)

# Create homomorphic encryption context
context = SEALContext(params)

# Create key generator
keygen = KeyGenerator(context)
public_key = keygen.public_key()
secret_key = keygen.secret_key()

# Create encryptor and decryptor 
encryptor = Encryptor(context, public_key)
decryptor = Decryptor(context, secret_key)

# Encrypt Data
plaintext = Plaintext("42")
ciphertext = Ciphertext()
encryptor.encrypt(plaintext, ciphertext)

# Perform homomorphic addition
addend = Plaintext("15")
encryptor.encrypt(addend, ciphertext)
ciphertext += ciphertext

# Perform homomorphic multiplication
multiplier = Plaintext("7")
encryptor.encrypt(multiplier, ciphertext)
ciphertext *= ciphertext

# Decrypted Result
result = Plaintext()
decryptor.decrypt(ciphertext, result)
print("Decrypted result:", result.to_string())