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2021picoctfsolutions.compicoCTF

picoCTF 2021

86 challenges with 86 published solutions between them. Solution links go to picoctfsolutions.com, which is the only writeup source this index uses for picoCTF - one worked solution per challenge, rather than an aggregate of other people’s posts.

Every writeup on picoctfsolutions.com

Cryptography17

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 decoderVigenere cipher solver with automatic key recoveryRSA decryption and attack runnerWiener’s attack on small RSA private exponentsIn-browser hash cracker with rule transformsLearn: Classical ciphers and frequency analysisLearn: RSA and the parameters that break it

Web17

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 verifierJWT alg=none bypass generatorWeb attack payload catalogJWT secret brute forceLearn: Web attacks and session tokens

Binary exploitation16

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 finderShellcode assembler and libraryCyclic pattern generator and offset finderFormat string exploit builderLearn: Binary exploitation

Reverse engineering16

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 blobsWebAssembly disassemblerJava .class disassemblerPython .pyc bytecode disassemblerLearn: Binary exploitation

Forensics13

Recover something from a file, a capture, or a disk image - often from a part of it the format says is unused.

Solve it with:File type identifier by magic bytesMagic byte and file signature tablePCAP analyzer for CTF network forensicsEXIF metadata viewerLearn: File forensics and carvingLearn: Network forensics

  • Disk, disk, sleuth!

    1 writeup
    • disk-forensics

  • Disk, disk, sleuth! II

    1 writeup
    • disk-forensics

  • Information

    1 writeup
    • metadata-analysis

  • MacroHard WeakEdge

    1 writeup
    • steganography

  • Matryoshka doll

    1 writeup
    • steganography
    • file-carving

  • Milkslap

    1 writeup
    • steganography
    • lsb-stego

  • Surfing the Waves

    1 writeup
    • audio-stego

  • Trivial Flag Transfer Protocol

    1 writeup
    • pcap-analysis
    • steganography

  • tunn3l v1s10n

    1 writeup
    • image-analysis
    • hex-analysis

  • Very very very Hidden

    1 writeup
    • steganography

  • Weird File

    1 writeup
    • file-inspection
    • file-magic

  • Wireshark doo dooo do doo...

    1 writeup
    • pcap-analysis

  • Wireshark twoo twooo two twoo...

    1 writeup
    • pcap-analysis

Misc7

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 decoderCipher identifier and automatic decoderRegex tester with match offsets and capture groupsLearn: Recognising encodings

Other 2021 events