Brief solution ideas to the least solved Crypto CTF challenges.
I made a RSA signature box, but the hardware is too old that sometimes it returns me different answers… can you fix it for me?} e = 0x10001 nc crypto.chal.csaw.io 8002 Summary: fault attack on RSA signatures, factoring using private exponent exposure.
Decrypt the cipher text with a pinhole. $ nc cry1.chal.ctf.westerns.tokyo 23464 pinhole.7z Summary: attacking RSA using decryption oracle leaking 2 consecutive bits in the middle.
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)
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?
Since I needed to sign a document I thought about doing it with a Chinese paintbrush… Too bad my hand is not that steady, so just in case, I re-signed it with a common pen. Sadly I keep being forgetful, so I actually forgot where I left the two halves of the sigil I used …
The Dobbertin Challenge is issued every two years since 2006, in honor and memory of Prof. Hans Dobbertin. http://cryptochallenge.nds.rub.de:50080/ A simple JSON Web Service is provided, which processes PIN codes of users. A user can send his encrypted PIN to the Web Service, which decrypts and stores the PIN. The Web Service allows to use …