RSA part 1

rsa.md

RSA Challenge

• chc.cs.cornell.edu:1352

• Code: https://gist.github.com/tjade273/36455f4955307db2b680c4f1ac35e710#file-rsa-c

The server accepts any 1024 bit RSA ciphertext, base64 encoded, and decrypts it using the private key corresponding to:

• RSA Public Key:

  -----BEGIN PUBLIC KEY-----
  MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCvP/QCbo6bihIPrf68zjsJXZ6g
  1qVzxK9SQo94CwsY10kSjwddz2inke18YE5AYnnhqLMb8CnyuHIplpCvr6av5kdP
  Va5BtrUVzockQYovnrzASif4gccPfZYrvaiRbTwUNLyF/S0Lb2Y5vFwPPw95VaEo
  WJ3d1vNm5Fh9oShGiwIDAQAB
  -----END PUBLIC KEY-----
  

• Encrypted Flag (base64):

  bXqnLSa8E8KbD3A/isI7++FNAFTXH6nF184TKUaQBePapvPfcnlZ782mDuMwL4E7Be57HcGBOFMIU/3ALuxq2+cUlyMK07jEU1vdJDbUgXbc3wEbJtWHbs1Y3DJb+DCi9PiDZplE2G1nAXkQQWTuv2+dCv6pUFRgWeocQty8y/s=
  

Example usage

cat  <(head -c 118 /dev/zero) <(echo -n -e "testing...") |
openssl rsautl -encrypt -raw -pubin -inkey key.pub |
openssl base64  -A | xargs echo | nc chc.cs.cornell.edu 1352

The goal is to decrypt the flag. Good luck!