Problem 44956. Determine RSA keys (public and private) given two prime number character strings (p and q)

Created by David Hill

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119 Solutions
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Last Solution submitted on Apr 07, 2022

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Tim on 28 Aug 2019

I get different results for d in test cases 2, 3, and 4 (in particular, d=929660805638728623653 for test case 2).

David Hill on 28 Aug 2019

This was my first Cody problem and I had a mistake in the assert within the test cases. I fixed the problem. Previously the assert was looking for [n,d] combined into a single character array. I have tested the test cases and they are correct. You should use the Euclidean algorithm.

Tim on 28 Aug 2019

If I understand correctly, we should have mod(d*e,phi)=1, where phi=(p-1)*(q-1). My answers seem to satisfy that condition, but test cases 2, 3, and 4 do not.

David Hill on 28 Aug 2019

Tim, you are absolutely correct. Thanks for the comment. I fixed the test cases.

Joel Hottinger on 9 Jul 2021

Could someone help me out with the modular inversion. I can't seem to get it to work for any large numbers. I've been stuck for a while

Joel Hottinger on 9 Jul 2021

I think my main issue is that I cannot use the mod function with large numbers, what is a way around this?

David Hill on 27 Jul 2021

look at importing java biginteger

Joel Hottinger on 28 Jul 2021

@David Hill. Thanks, that worked a lot better for me

Jeremy Perez on 6 Aug 2021

One should first consider if MATLAB is even adapted for these kinds of calculations. Still, I had a lot of fun.

Solution Comments

Solution 1915449

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2 Comments

Tim on 29 Aug 2019

Googling can supplant programming sometimes.

Khanh Dao on 12 Mar 2022

:<<

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cryptography large integer calculations

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Problem 44956. Determine RSA keys (public and private) given two prime number character strings (p and q)

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Problem 44956. Determine RSA keys (public and private) given two prime number character strings (p and q)

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Last 200 Solutions

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Problem Recent Solvers12

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