tl;dr

• Extract higher bits of secret using input manipulation
• Extract lower bits of secret using the highers bits and input manipulation

tl;dr

1. Find the co-relation between variables in the LFSR equation
   1. d == out (75%)
   2. a == b (75%)
   3. c^d == out (75%)
   4. (d!= out) => (c==1) always
2. Solve for the seed using 2000 output bits
3. Try out which among the four possible combinations decrypt the flag

Intended solution of PRetty stroNG challenge from InCTF Internationals 2019

tl;dr

• Recover sample outputs from PRNG
• reverse wrapper function
• find seed from outputs
• get the flag

Intended solution of waRSAw challenge from InCTF Internationals 2019

tl;dr variant of LSB Oracle Attack on unpadded RSA

tl;dr

1. Find Elliptic Curve parameters from given points on the curve
2. Find x-coordinate of 2*P, given y-coordinate of 2*P
3. Invert 2 over mod (P.order()) and multiply the result with 2*P to get P
4. Submit ASIS{P.x} as the flag

Full solution of EZDSA challenge from MidnightSun CTF Quals 2019.

tl;dr retrieving key using Euler’s Criterion to break signature authentication

tl;dr solving RSA Digital Signature using it’s homomorphic property:

1. Calculate the signature of factors of message M to be signed, separately
2. Combine them by multiplication over modulus to get the signature of M

tl;dr Coppersmith’s Attack to recover RSA primes

tl;dr

1. Find roots in a polynomial ring over $ mod;p $
2. Use Hensel’s Lifting lemma to find roots over $ mod;p^k $

tl;dr Known plaintext attack on a multithreaded AES-CTR