Score:3

In a public-key system using rsa, you intercept the ciphertext c = 15 sent to a user whose public key is e = 5, n = 35. What is the plaintext m?

ec flag

In a public-key system using rsa, you intercept the ciphertext c = 15 sent to a user whose public key is e = 5, n = 35. What is the plaintext m?

In my calculations m=15. But i dont think my calculations are correct

DannyNiu avatar
vu flag
Good study question. Let's see your calculation steps so that we can help you correct the mistake.
DannyNiu avatar
vu flag
Also, small modulus such as yours may have some "fixed points", i.e. cipher transcripts that encrypt and decrypt to themselves.
ec flag
[5*d][mod(24)]=1. So d=5; based on this , 15^5 mod(35) = 15
DannyNiu avatar
vu flag
Good, it's correct. This is the exact "fixed point" I was talking about. I confirmed this using Python.
DannyNiu avatar
vu flag
The next time you have doubt, try some other numbers.
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