破解加密数据

备注

某工控厂商自行研发了一套加密系统，这样的话只要不是系统内部人员，即使数据被窃听没关系了。你截获了一段密文：109930883401687215730636522935643539707，请进行解密

flag 形式为 flag{}

ChatGPT 直接秒了

先分析加密脚本

m = "unknown"
e = 2
n = 0x6FBD096744B2B34B423D70C8FB19B541

assert(int(m.encode('hex'), 16) < n)
c = pow(int(m.encode('hex'), 16),e,n)
print c

典型的 RSA 加密问题

$$c = m^e \mod n$$

求解 m 的可能值

from sympy import mod_inverse, isprime, sqrt_mod

# Given values
c = 109930883401687215730636522935643539707
n = 0x6FBD096744B2B34B423D70C8FB19B541
e = 2

# Check if c has a modular square root under n
try:
    # Compute the modular square root of c mod n
    m_values = sqrt_mod(c, n, all_roots=True)
except ValueError:
    m_values = None

m_values

# [31698494966724069351424094257, 47966037907531568164415165899182644837, 100559804454305364139582472308130223836, 148525842330138437337273568855888774416]

尝试还原出字符串

# Function to convert a number to a hex string and then decode it as text
def number_to_string(num):
    try:
        # Convert to hex, remove the '0x' prefix, and decode to ASCII
        hex_str = hex(num)[2:]  # Remove '0x' prefix
        if len(hex_str) % 2 != 0:  # Make sure it's even-length for decoding
            hex_str = "0" + hex_str
        return bytes.fromhex(hex_str).decode('utf-8', errors='ignore')  # Decode ignoring invalid characters
    except Exception:
        return None

# Attempt to decode each candidate for m
decoded_strings = [number_to_string(m) for m in m_values]
decoded_strings

即可得到答案

flag{flag_EnCryp1}