2021weight 24.70InfoSecIITR

BackdoorCTF 2021

4 challenges with 5 published community solutions between them. Solution links go to CTFtime’s task page, which aggregates every writeup for a challenge - individual blog posts rot, the aggregator does not.

Full task list on CTFtime

Cryptography2

Recover a plaintext or a key from something that was supposed to protect it. In practice: identify the scheme, find the parameter the author got wrong, exploit it.

Solve it with:Cipher identifier and automatic decoder Vigenere cipher solver with automatic key recovery RSA decryption and attack runner Wiener’s attack on small RSA private exponents In-browser hash cracker with rule transforms Learn: Classical ciphers and frequency analysis Learn: RSA and the parameters that break it

beyond the mountain
500 pts1 writeup
- crypto
Same technique in picoCTF: StegoRSA, Timestamped Secrets, AES-ABC
NonAbelian
500 pts1 writeup
- misc
- crypto
Same technique in picoCTF: StegoRSA, Timestamped Secrets, AES-ABC

Binary exploitation1

Turn a memory-safety bug in a native binary into control of execution. Usually a stack overflow, a format string, or a heap primitive.

Solve it with:ROP gadget finder Shellcode assembler and library Cyclic pattern generator and offset finder Format string exploit builder Learn: Binary exploitation

Baby heap
436 pts2 writeups
- heap
- integer_overflow
- use-after-free
Same technique in picoCTF: tea-cash, sice_cream, zero_to_hero

Misc1

Everything that fits no other box: esolangs, puzzles, scripting exercises, and the jail escapes that have not yet earned their own category.

Solve it with:Brainfuck and esolang decoder Cipher identifier and automatic decoder Regex tester with match offsets and capture groups Learn: Recognising encodings

SCAndal
1 writeup
Same technique in picoCTF: Permissions, Specialer, Codebook

Cryptography2

beyond the mountain

NonAbelian

Binary exploitation1

Baby heap

Misc1

SCAndal

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