Brute-force to Caesar’s cipher

Breaking Caesar’s cipher with Brute-force

"""
Brute-force the following Caesar’s cipher, and find
the plaintext and key of the following
message: kyvtrmrcipnzccrkkrtbwifdkyvefikynvjkrkeffe
"""

alphabet = "abcdefghijklmnopqrstuvwxyz"

def encrypt(plaintext, k):
    ciphertext = []
    for c in plaintext:
        i = alphabet.index(c)
        j = (i + k) % len(alphabet)
        ciphertext.append(alphabet[j])
    return ''.join(ciphertext)


def decrypt(ciphertext, k):
    return encrypt(ciphertext, -k)


def brute_force(ciphertext):
    plaintext = []
    plaintexts = {}
    for key in range(26):
        for c in ciphertext:
            i = alphabet.index(c)
            j = (i - key) % len(alphabet)
            plaintext.append(alphabet[j])


        plaintexts[''.join(plaintext)] = key
        plaintext = []


    for plaintext, key in plaintexts.items():
        print(plaintext + ": " + str(key))
    

brute_force("kyvtrmrcipnzccrkkrtbwifdkyvefikynvjkrkeffe")