Cody

Rafael S.T. Vieira

4
Rank
86
Badges
39578
Score
1 – 50 of 5,865

Rafael S.T. Vieira submitted a Comment to Problem 44971. Convert base 10 to base x (2-16)

Oh, the problem was with my algorithm, sorry. I am indeed using python's long int (for multiplication of large integers), but I was relying on str2num for some operations (which apparently introduced floats back in my code). After removing it, it worked out fine. PS: This new update knocked out some wrong solutions (including some of mine). Awesome. :)

2 hours and 15 minutes ago

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

Thanks, David. I've struggled for a while with this problem but I've finally figured it out. First, although we don't use the encryption function from 7.1.1, we must create an output EM of length k-1 and apply a pad of 0 as the first character of EM (It was strange to see all hashes starting with 0). Next, I was confused with the Feistel Network, because my MGF from the previous problem wasn't working (an accepted solution), but I realized that you were probably using a hex input, instead of char (which is weird since the MGF function requires an Octect String as input), but anyway that solved it. :)

2 hours and 24 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 2451. BLOCK x3 (Version 1)

https://noodlecake.com/games/blockblockblock/ (The game is no longer available at Google Play).

4 hours and 58 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 1015. Polynomial Interpolation

FYI: The condition number of the Vandermonde coefficient matrix is just the norm of the matrix times the norm of its inverse. Cheers. PS: Wikipedia will just lead you to a paid wall. Don't waste time.

5 hours and 23 minutes ago

Rafael S.T. Vieira submitted a Comment to Problem 44971. Convert base 10 to base x (2-16)

It seems the precision issues were indeed fixed. :)

10 hours and 28 minutes ago

Rafael S.T. Vieira liked Problem 45362. RIPEMD160 Hash

16 hours and 30 minutes ago

Rafael S.T. Vieira submitted Solution 3376633 to Problem 45362. RIPEMD160 Hash

16 hours and 30 minutes ago

Rafael S.T. Vieira submitted Solution 3370408 to Problem 45320. SHA256 Hashing

23 hours and 37 minutes ago

Rafael S.T. Vieira submitted Solution 3370388 to Problem 45320. SHA256 Hashing

23 hours and 38 minutes ago

Rafael S.T. Vieira submitted Solution 3370373 to Problem 45320. SHA256 Hashing

23 hours and 39 minutes ago

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

23 hours and 43 minutes ago

Rafael S.T. Vieira liked Problem 45320. SHA256 Hashing

23 hours and 45 minutes ago

Rafael S.T. Vieira submitted Solution 3370293 to Problem 45320. SHA256 Hashing

23 hours and 45 minutes ago

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

on 25 Oct 2020 at 5:13

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.

on 24 Oct 2020 at 21:47

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?

on 24 Oct 2020 at 20:08

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.)

on 24 Oct 2020 at 13:50

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).

on 24 Oct 2020 at 12:56

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

1 – 50 of 5,865