CTemplar Checksum Implementation

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Encrypted Email Services Can Hack You Using JavaScript

JavaScript can be used to serve malicious code, exploits, or hacks. This is illustrated by GizmodoUSENIXAsk LeoStack Exchange, ITNEXT, and it is a recurring theme at the hacker conference DEFCON. JavaScript hacks are also the primary way to de-anonymize Deep Web users.

In November of 2018, Professor Kobeissi revealed that if JavaScript is required for encryption, it can also be used to hack users who use end-to-end encrypted email services. In January of 2019, one end-to-end encrypted email service, ProtonMail, publicly stated that they are capable of hacking their users and decrypting all of its user’s data through JavaScript. This post showed their dedication to the people who use their service. We have written a post expressing our gratitude to Proton Technologies AG for the work they have done in the security ecosystem here.

Does having open-source code eliminate this risk? No, because open-source code is just an act to encourage users’ trust. The audited code in GitHub might not be the same code that is sent to you from a companies private server. There is no assurance or promise that the code hosted is the same as the one is served.

Currently, all end-to-end encrypted email services can hack their users and decrypt all of their data except us. We can provide this level of protection using an implementation of checksums that haven’t been used before. We are proudly the first “Zero Access” end-to-end encrypted email service that is not able to decrypt our own user’s emails.

How Did We Solve This With Checksums?

Our checksum implementation allows our users to compare the code served to their browser with the code in GitHub within 15-30 seconds. Usually, comparing code can take hours or days. With checksums, you can do it in seconds.

First, the file index.html starts the platform loading process and determines what is loaded, but when doing so, could pose a couple of risks:

  1. Someone/Something could modify the JavaScript files defined in the “index.html” making them harmful without the user’s knowledge.
  2. Someone/Something could make “index.html” load more JavaScript files than what the authors intended, making the website harmful to the users without the user’s knowledge.

In any case, if anyone wants to manually verify if our “index.html” hasn’t been tampered and is the same as the one being served, we have a guide in GitHub.

At the time of writing, our current checksum is:

SHA-256 checksum of “index.html”:


The CTemplar Team:

Disclaimer: Checksums do not protect you from hacks from your browser, OS’s, plugins, mobile ISP providers, running process software, or the Intel Microprocessor hardware backdoor. We do not protect against keyloggers that may be installed on your computer.

Godfrey De Saint Omer

Godfrey De Saint Omer

Godfrey de Saint Omer enjoys security/security and loves the community. He welcomes comments or suggestions to the platform because he feels like many of the best comments come from average users.

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