The user of Habr, one of the largest Russian-speaking IT media, under the nick Scratch was able to find out a vunerability in Telegram Passport, an ID service from the developers of popular messanger. The vulnerability allows to steal users' personal data. It is caused by the encrypting algorithms, which are used by the solution.This is reported by Security Lab.
As reported, in fact, the encryption in Telegram Passport is not end-to-end in the usual sense, but a specially developed algorithm. Encrypted personal data and an almost random cryptographic key, as well as a hash from personal data, mixed with random bytes, are transmitted to the cloud storage. Scratch says that this information is enough to conduct a successful brute-force attack and to steal personal data of users of the service.
This is by no means a "random noise", it has everything necessary, including an encryption key protected by password. And it allows you to get to user data much, much faster than sorting out all possible combinations of AES keys (2 ^ 256). Also, such mechanisms invented by the authors of Telegram as a validation of the key with the help of the sum of bytes, the involvement of the data itself in the formation of the key of their own encryption and the data hash instead of HMAC are also highly questioned.
The developer described in detail all the algorithms that the service uses to provide encryption, and also described an approximate plan for using bruteforce attack to hack the service. In addition, he cited several services that use "real" end-to-end encryption. Among them - the messengers Signal and Whatsapp.
In addition, the security expert noted that the speed of hacking depends on the length of the user's password. For protection, he proposed to come up with a complex password longer than 8 characters, which, in his opinion, uses a very small number of users.
The tool for fast authentication and storage of user data Telegram Passport officially came out on July 26, 2018. It has already been criticized for security policy by Anton Rosenberg, the former colleague of the creator of the Telegram, Pavel Durov.