Cody

Rafael S.T. Vieira

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Rafael S.T. Vieira submitted a Comment to Problem 45320. SHA256 Hashing

The hardest thing is to use a hexadecimal input. Most on-line sites deal only with text. Exception: https://emn178.github.io/online-tools/sha256.html

9 minutes ago

Rafael S.T. Vieira liked Problem 45347. Cat's paw - 01

3 hours and 22 minutes ago

Rafael S.T. Vieira submitted Solution 3369023 to Problem 45347. Cat's paw - 01

3 hours and 23 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 46669. Rotation matrix of a sequence of 3D points

Please, do not use isequal with floats, prefer instead abs(a-b) < tol. Notice how my solution used round and had to fix errors manually despite the operation being correct.

10 hours and 48 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 44964. Optimal Asymmetric Encryption Padding of message for RSA Cryptography

Hi, David, is the problem description right? Seems that section 9.1.1 has the EME-OAEP-encode/decode pair, while 7.1.1 is another function that uses EME-OAEP, but it is not it. Moreover, how do we apply the Feistel network inside the MGF1 (disjoint sets or with intersection: 1,1,2,2,3,3,..., n n or 2 3 4 .. .n 1)? And how many rounds? 2 or more? Should the Feistel network replace the MGF1 function? Could you, please, explain?

12 hours and 27 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 46025. Evaluate the gamma function

I've found a 1968-paper by Wrench, Concerning Two Series for the Gamma Function, which gives us the 20th first terms of one formula for instance. https://www.ams.org/journals/mcom/1968-22-103/S0025-5718-1968-0237078-4/ (It would be more than enough if there weren't issues with all approximations.)

18 hours and 45 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 46025. Evaluate the gamma function

Several formulas can approximate the gamma function on the complex domain, but all of them have issues. Please, look at its plot before starting. Nonetheless, there is a trick that makes them all work; and you must find it (I've lost some time trying different formulas, adding more terms, but it is not the way to go).

19 hours and 39 minutes ago

Rafael S.T. Vieira submitted a Comment to Solution 2660459

It took me a while to realize the same thing...

on 24 Oct 2020 at 7:48

Rafael S.T. Vieira submitted a Comment to Problem 44963. Mask Generation Function (MGF1) for PKCS #1 Standard utilizing Optimal Asymmetric Encryption Padding for RSA Cryptography

For anyone trying this problem, you will probably have to implemment I2OSP too from the documentation, which is a function to convert a decimal number to base 256 of fixed length. Follow the specs to the letter.

on 24 Oct 2020 at 1:03

Rafael S.T. Vieira submitted a Comment to Problem 44961. RSA decryption

Similar to the first https://www.mathworks.com/matlabcentral/cody/problems/44959-rsa-encryption-using-public-key It is necessary to convert the number obtained back from base 256 to base 10.

on 23 Oct 2020 at 22:44

Rafael S.T. Vieira liked Problem 44961. RSA decryption

on 23 Oct 2020 at 22:42

Rafael S.T. Vieira submitted a Comment to Problem 44959. RSA encryption using public key

A better answer to William (and for people that don't use Java) would be that after converting numbers to uint8, we must transform a vector into a single number using base 256. That means that a word like 'ball' becomes [98, 97, 108, 108] and then 98*256^3 + 97*256^2 + 108*256 + 108 = 1650551916.

on 23 Oct 2020 at 20:56

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