write up ctf by ariafatah

ariaf.my.id/ctf_aria/cryptography/M_un_Mini RSA.html


soal

What happens if you have a small exponent? There is a twist though, we padded the plaintext so that (M ** e) is just barely larger than N. Let’s decrypt this: ciphertext

hint

  • RSA tutorial
  • How could having too small of an e affect the security of this key?
  • Make sure you don’t lose precision, the numbers are pretty big (besides the e value)
  • You shouldn’t have to make too many guesses
  • pico is in the flag, but not at the beginning

solve

wget https://mercury.picoctf.net/static/a24cf907007a19dbf30310acad0df9e5/ciphertext


flag