凯撒密码(Caesar)

# write by 2021/6/26
UPPER_DIC = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
LOWER_DIC = "abcdefghijklmnopqrstuvwxyz"
def encrypt_caesar(string, offset):
    ciphertext = ""
    for i in string:
        if i in UPPER_DIC:
            new_index = (UPPER_DIC.index(i) + offset) % 26
            ciphertext += UPPER_DIC[new_index]
        elif i in LOWER_DIC:
            new_index = (LOWER_DIC.index(i) + offset) % 26
            ciphertext += LOWER_DIC[new_index]
        else:
            ciphertext += i
    return ciphertext
def decrypt_caesar(string, offset):
    return encrypt_caesar(string=string, offset=26-offset)
if __name__ == '__main__':
    ciphertext = encrypt_caesar("Caesar is good!", 3)
    plaintext = decrypt_caesar(ciphertext, 3)
    print(f"{plaintext}: {ciphertext}")