Making online exams happen offline

The problem OffSubmit solves


  • Due to COVID, many institutes decided to conduct remote online open-book exams.
  • Internet speed in many parts of India is insufficient for downloading the question papers and submitting answer sheets in a quick time.
  • Students of Jammu & Kashmir also face a lot of problems due to no 4G services.
  • This caused a lot of students inconvenience and even to opt-out of the remote exams.


10 to 15 days before the exam, students will have to download the AES encrypted question papers of all exams collectively. Since now the student has sufficient time so there are no worries of slow internet speed.

Just before the beginning of each exam, the teacher will SMS the password to unlock that question paper and the app will decrypt the question paper so that students can now see it and start with the exam.

After writing the answer sheet, the student will create a pdf and the app will then create an SHA-256 hash of it and this hash will be sent as SMS from the student’s phone to Twilio no. and if the student has sent the SMS before the deadline of the exam, say 1 hour later, then this hash will be stored on the Ethereum-Matic chain corresponding to his id.

Now the previous process will be repeated for the remaining of the exams.

Once all the exams are over then the student can upload his answer sheets pdf taking an ample amount of time so that there is no inconvenience for slow internet speed users.

Now the app will check whether the student has uploaded the same answer sheets by matching the uploaded file’s hash and previously SMS hash stored on the Matic blockchain.

This will check that student has not tampered with the file after the deadline of the exam.

Now the professor can download the answer sheets and do the evaluation.

Unique Selling Points

  • The app can be scaled to an offline Moodle app for the exam.
  • The app does not use System time to keep track of submission as System time can be changed.

Challenges we ran into

  1. We figured out that file hash changes with file name so we have to come out with a protocol of always uploading and downloading with the file name as 'manual.pdf'.
  2. Since in mobile SMS, not more than 160 characters so we had to research that truncating the file hash does not reduce the hash security very much after which we truncated the hash from 64 to 45 characters.