def test_multiply():
private_key, public_key = create_key_pair(bit_length=TEST_BIT_LENGTH)
a = 123
b = 25
expected = (123 * 25) % public_key.n
ciphertext_a = encrypt(public_key, a)
encrypted_result = multiply(public_key, ciphertext_a, b)
result = decrypt(private_key, public_key, encrypted_result)
assert result == expected
def encrypted_celsius_to_fahrenheit(public_key: PublicKey,
ciphertext: int) -> int:
"""
Returns an encrypted integer representing 1/10ths of a degree Fahrenheit
°F = °C * 1.8 + 32
"""
# First multiply the ciphertext by 18.
multiplied_by_18 = multiply(public_key, ciphertext, 18)
# Now encrypt 320.
encrypted_320 = encrypt(public_key, 320)
# Finally add them together. The result will need to be divided by 10.
return add(public_key, multiplied_by_18, encrypted_320)
def test_multiply_by_one():
private_key, public_key = create_key_pair(bit_length=TEST_BIT_LENGTH)
a = 123
b = 1
expected = 123
ciphertext_a = encrypt(public_key, a)
naive_encrypted_result = ciphertext_a
encrypted_result = multiply(public_key, ciphertext_a, b)
assert encrypted_result != naive_encrypted_result
result = decrypt(private_key, public_key, encrypted_result)
assert result == expected
def encrypted_price_calculator(
public_key: PublicKey,
# a list of (encrypted price, plaintext quantity) tuples
encrypted_cart: List[Tuple[int, int]],
) -> int:
"""
Returns the encrypted sum of multiplying each encrypted price by an unencrypted quantity
"""
item_subtotals = [
multiply(public_key, price, quantity)
for price, quantity in encrypted_cart
]
total = encrypt(public_key, 0)
for item_subtotal in item_subtotals:
total = add(public_key, total, item_subtotal)
return total