2015weight 0.00SiBears

School CTF 2015

5 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

Cryptography1

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

Lazy cryptanalyst
100 pts1 writeup
- crypto
Same technique in picoCTF: StegoRSA, Timestamped Secrets, AES-ABC

Web1

Reach data or functionality the application meant to keep from you - through its inputs, its tokens, or its trust in the client.

Solve it with:JWT decoder and signature verifier JWT alg=none bypass generator Web attack payload catalog JWT secret brute force Learn: Web attacks and session tokens

Awesome web
200 pts1 writeup
- admin
Same technique in picoCTF: Client-side-again, dont-use-client-side, Irish-Name-Repo 3

Reverse engineering1

Work out what a compiled program does without its source, then work backwards from the check to the input that passes it.

Solve it with:Strings extractor for binaries and blobs WebAssembly disassembler Java .class disassembler Python .pyc bytecode disassembler Learn: Binary exploitation

Parallel Comparator
200 pts1 writeup
- engeneering
- reverse engineering
Same technique in picoCTF: WinAntiDbg0x100, WinAntiDbg0x200, WinAntiDbg0x300

Steganography1

Find the payload hidden inside a carrier that looks ordinary. Bit planes, appended data, metadata, and audio spectrograms.

Solve it with:LSB steganography extractor PNG chunk analyzer Audio spectrogram and SSTV decoder Zero-width character and text steganography decoder Learn: Steganography

Pure color
100 pts1 writeup
- stegano
Same technique in picoCTF: FindAndOpen, StegoRSA, Glory of the Garden

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

Highly professional
100 pts1 writeup
- joy
Same technique in picoCTF: Permissions, Specialer, Codebook

Cryptography1

Lazy cryptanalyst

Web1

Awesome web

Reverse engineering1

Parallel Comparator

Steganography1

Pure color

Misc1

Highly professional

Other 2015 events