Apr
18

PlaidCTF 2016 – Radioactive (Crypto 275)

We just got this fancy new cryptographic device and it seems to work great… for the most part. But sometimes the values it gives me are wrong. Maybe you could take a look for me. radioactive.tar.bz2 Summary: fault attack on RSA signature (not RSA-CRT)

Mar
14

0CTF 2016 Quals – Equation (Crypto 2 pts)

Here is a RSA private key with its upper part masked. Can your recover the private key and decrypt the file? equation.zip Summary: recovering RSA key from part of the private key.

Mar
13

0CTF 2016 Quals – RSA? (Crypto 2 pts)

It seems easy, right? rsa.zip Tip: openssl rsautl -encrypt -in FLAG -inkey public.pem -pubin -out flag.enc Summary: factoring 300-bit modulus into 3 primes, extracting cube roots.

Mar
07

Boston Key Party CTF 2016 – Feistel (Crypto 5pts)

feistel – 5 – 15 solves : crypto: I just made a brand new cipher! Can you recover the key? 52.86.232.163:32785 feistel.go Summary: slide with a twist attack

Mar
07

Boston Key Party CTF 2016 – GCM (Crypto 9pts)

[8] : gsilvis counting magic – 9 – 4 solves : crypto: Here’s a verification/decryption server: gcm.ctf.bostonkey.party:32768 . Get the GCM MAC key (the thing the server prints out on startup). We’ve given you one valid ciphertext to get you started. It has iv: [102 97 110 116 97 115 116 105 99 32 105… Continue reading »

Mar
07

Boston Key Party CTF 2016 – HMAC-CRC (Crypto 5pts)

[3] : hmac_crc – 5 – 36 solves : crypto: We’re trying a new mac here at BKP—HMAC-CRC. The hmac (with our key) of “zupe zecret” is ‘0xa57d43a032feb286’. What’s the hmac of “BKPCTF”? hmac-task.py Summary: breaking HMAC-CRC (again)

May
27

CONFidence CTF 2015 – RSA2 (Crypto 500)

Find the flag data Summary: cube attack + recover python’s MersenneTwister state + leak 320/520 LSBs of one of the primes

May
27

CONFidence CTF 2015 – RSA1 (Crypto 400)

Find the flag data Summary: Coppersmith’s short pad attack

May
11

ASIS CTF Quals 2015 – Cross Check (Crypto 350)

The flag is encrypted by this code, can you decrypt it? crosscheck.tar.xz Summary: breaking RSA modulos with related primes.

May
04

VolgaCTF Quals 2015 – CPKC (Crypto 400) writeup

cpkc A home-brewed cryptosystem, should be easy to break. Its keyspace seems to be rather large though… challenge.tar Summary: LLL-based attack on NTRUEncrypt-like cryptosystem.

Apr
20

PlaidCTF 2014 wheeeee writeup

Although it seems like The Plague’s messaging service is secure, there are bound to be bugs in any 20th century crypto system. We’ve recovered a version of the block cipher The Plague implemented. Use their online encryptor tool, at 54.82.75.29:8193, to break the cipher and figure out Plague’s secret plans. NOTE: When the service sends… Continue reading »

Apr
18

PlaidCTF 2014 __nightmares__ writeup

The Plague is building an army of evil hackers, and they are starting off by teaching them python with this simple service. Maybe if you could get full access to this system, at 54.196.37.47:9990, you would be able to find out more about The Plague’s evil plans. Code: (can be run locally with $ socat… Continue reading »

Apr
17

PlaidCTF 2014 RSA writeup

Our archaeologists recovered a dusty and corrupted old hard drive used by The Plague in his trips into the past. It contains a private key, but this has long since been lost to bitrot. Can you recover the full key from the little information we have recovered?

Mar
02

Boston Key Party CTF – Differential Power (Crypto 400)

we hooked up a power meter to this encryption box. we don’t know the key. that’s what we want to know. you can encrypt any string of 8 characters on the service http://54.218.22.41:6969/string_to_encrypt encrypt.asm chall source (released after ctf)

Feb
24

Codegate 2014 Quals – Angry Doraemon (pwn 250)

□ description ========================================== OS : Ubuntu 13.10 x86 IP : 58.229.183.18 / TCP 8888 http://58.229.183.26/files/angry_doraemon_c927b1681064f78612ce78f6b93c14d9 ========================================== □ number of solvers : 57 □ breakthrough by 1 : More Smoked Leet Chicken (02/23 06:16) 2 : ppp (02/23 06:22) 3 : stratumauhuur (02/23 06:28) Binary

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