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.