# BlackAlps 2019 - RSA

*RSA signing messages interface. Applying the Wiener attack reveal the private key which is the flag.*

*RSA signing messages interface. Applying the Wiener attack reveal the private key which is the flag.*

*Schnorr signature with a Blum-Blum-Schub PRNG to generate the nonce. Since the quadratic equation can be solved in the prime group the private key can be recover from two consecutive signatures.*

*Reverse challenge which is finally a maze. A move is encoded on 2 bit of a character given as input. The combination which gets you out of the maze is the flag. We present here three different ways to solve the challenge.*

*RSA encrypted flag but each flag bit is encrypted at a time with random padding. The padding is a square thus using computing the Jacobi symbol for each bit encryption reveals the flag.*

*RSA encrypted flag and prime inverses are given*

*A serial connection gives access to a basic filesystem. Repairing the filesystem with debug tools and adjusting an offset gives access to protected data.*