This challenge was solved by @R3x and @d3xt3r during the CTF. Writeup by @R3x The challenge has two files - an Linux 64 bit executable and a encrypted file. Reversing the executable Running the executable we notice that it takes two command line arguments. The first argument is the input file and the second is... Continue Reading →

This challenge was solved by @R3x and @sherl0ck. This writeup is written by @R3x. The challenge binary was slightly obfuscated. On reversing it we found that the algorithm for encryption was as such. The VM loads a key from the program it's running. The input file is divided into 64 bit blocks Each blocked with the... Continue Reading →

Write-ups of various crypto challenges from Volga CTF Qualifier 2019

Solved by @slashb4sh, @sherl0ck, and @night_f0x This weekend had a couple of really good CTF's, iCTF and Teaser CONFidence CTF, and our team had loads of fun playing them. In the Teaser CONFidence CTF, there was this really fun kernel challenge which is extremely beginner friendly. This was also the first time me and sl4shb4sh took... Continue Reading →

Writeups of all crypto challenges from CONFidence Teaser CTF 2019

Relations Solved by: D1X1T, 4lph4, v3ctor, nsg99, s0rc3r3r  This was a fairly easy challenge although we are not given any encryption script. We are given three operations on the nc service to choose, XOR, ADD and DEC (decrypt). Then, we have to give an input string on which the selected operation is done. How the... Continue Reading →

Solved by sherl0ck I found this challenge the best challenge in this CTF and used the House of Orange to solve it. I dunno whether there is an easier way to solve this. Anyway, the binary that was provided was 64-bit non stripped and dynamically linked one. Here are the mitigations that were imposed on the binary... Continue Reading →

Solved by sherl0ck For this challenge, we were given a 64-bit stripped and dynamically linked binary. The given libc was version 2.24, that has some checks that its predecessors did not have. Let's start by looking at the mitigation's enforced on the binary - gdb-peda\$ checksec CANARY : ENABLED FORTIFY : disabled NX : ENABLED... Continue Reading →

Solved by sherl0ck This was my first challenge that involved the shared memory object concept and I found it pretty interesting to solve. The provided binary began to segfault after an initial run and I contacted the admins who promptly addressed the issue and released an update for this challenge. The shared object was not... Continue Reading →

Solved by sherl0ck Firstly, kudos to the organizers for conducting such a quality CTF. Coming to this particular challenge, we were given the libc and the binary. The following were the mitigation's enforced on the binary- gdb-peda\$ checksec CANARY : ENABLED FORTIFY : disabled NX : ENABLED PIE : disabled RELRO : Partial Reversing this... Continue Reading →