49 lines
No EOL
1.4 KiB
Python
49 lines
No EOL
1.4 KiB
Python
# pip install pycryptodome
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import time, json
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from Crypto.Util import number
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log=[]
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def blum_prime(bits): # p ≡ 3 (mod 4)
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while True:
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p = number.getPrime(bits)
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if p % 4 == 3: return p
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def keygen(bits=512, ttl=10):
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p, q = blum_prime(bits//2), blum_prime(bits//2)
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k = {"p":p, "q":q, "n":p*q, "exp":time.time()+ttl, "revoked":False}
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log.append({"t":time.time(), "ev":"KEYGEN", "n":k["n"]}); return k
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def publish(k):
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log.append({"t":time.time(), "ev":"PUBLISH", "n":k["n"]}); return k["n"]
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def revoke(k):
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k["revoked"] = True; log.append({"t":time.time(), "ev":"REVOKE"})
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def expired(k): return time.time() > k["exp"]
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def renew(k, ttl=10):
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revoke(k); k2 = keygen(bits=k["n"].bit_length(), ttl=ttl)
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log.append({"t":time.time(), "ev":"RENEW"}); return k2
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def enc(m, n): return pow(m, 2, n) # c = m^2 mod n
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def dec(c, k): # return one root via CRT (Rabin has 4 roots)
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p, q, n = k["p"], k["q"], k["n"]
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mp, mq = pow(c, (p+1)//4, p), pow(c, (q+1)//4, q)
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yp, yq = number.inverse(p, q), number.inverse(q, p)
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return (mp*q*yq + mq*p*yp) % n
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# Demo
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k = keygen(ttl=2); n = publish(k)
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m = 123456789
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c = enc(m, n); m1 = dec(c, k)
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print("ok:", m == m1)
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time.sleep(2.1) # simulate expiry
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if expired(k) or k["revoked"]:
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k = renew(k, ttl=5); n = publish(k)
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c2 = enc(m, n); m2 = dec(c2, k)
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print("ok2:", m == m2)
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print(json.dumps(log, indent=2)) |