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-1

If you mean perfectly secure, then YES OTP is indeed perfectly secure. But if you mean practically secure, then NO OTP is not practically secure. The reason is due to the fact that OTP requires usage of perfectly random numbers used as keys on both sides, however in practice using completely random keys is non-trivial, and usage of Pseudo Random Number ...


1

Is this secure? Yes, One-Time-Pads (OTPs) can be proven information theoretically secure. For a sketch of what this means and how to do this, please refer to this previous answer by me. Can I actually use modular addition as encryption like it said in Wikipedia? Yes, any group operation can be used to form a pefectly secret encryption scheme ...


1

Your idea of addition modulo 10000 is correct. The correctness follows from the fact that $\mathbb{Z}_{10000} = \{0, 1, \dots, 9999\}$ equipped with addition modulo $10000$ forms a (finite) group. Let $m \in \mathbb{Z}_{10000}$ denotes a PIN code. Now choose a uniformly random element $r \in \mathbb{Z}_{10000}$ and define $c = m + r \bmod 10000$. It is ...


5

In order for information-theoretic security to imply computational security, you need to require that the simulator run in time that is polynomial in the running time of the real adversary. This is the standard definition, specifically to avoid protocols such as you presented in your question. So, the answer is: If you allow the simulator to be unbounded ...



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