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Computer scientist wants to protect your texts

Saba Eskandarian designs online messaging applications that let users report abuses while preserving privacy.

Saba Eskandarian standing in front of code being projected behind him.
Carolina computer scientist Saba Eskandarian studies ways to secure online communications systems like Whatsapp and iMessage. (Megan Mendenhall/UNC Research)

Messaging applications that provide strong privacy regulations can have the unintended side effect of making it harder for users to report abuse.

Saba Eskandarian, an assistant professor in the College of Arts and Sciences’ computer science department, is dedicated to deciphering the problems that come with online messaging. He studies secure communication systems and applies his knowledge of cryptography — protecting information by shrouding it in codes — in new ways.

There are two types of major private messaging platforms: end-to-end encrypted and metadata-hiding.

When messages are end-to-end encrypted, the moderator no longer sees the message contents. An algorithm creates a binding tag for it. This identifier is specific, sent to the recipient along with the message — like a postmark on an envelope — and is readable by platform moderators if abuse is reported.

Currently, there are no effective techniques for doing this on metadata-hiding platforms — many of which are still prototypes but will hit the market soon. In metadata-hiding platforms, the moderator sees neither message contents nor the identities of message senders.

Message franking

Enter Eskandarian, who’s implementing new cryptographic approaches to design private messaging applications that allow users to report abusive content to the platform without compromising the privacy of other messages or conversations.

One tool he is looking at is message franking. First introduced by Facebook and used in both WhatsApp and Messenger Secret Conversations, it allows the receiver of a malicious message to report it to the moderator.

“If a user shows this tag to Facebook, Facebook can verify that it’s authentic, but if somebody else sees the tag, they cannot verify that it came from Facebook,” Eskandarian said. “This is helpful because it means that the platform itself can verify messages for moderation purposes, but users can’t just send messages to the government or the press to harm each other.”

He and his research team propose a shared franking technique, which would let the moderator authenticate messages sent through a metadata-hiding platform and tie them to their senders, despite only seeing content relevant to the report. This new application drastically decreases the time needed to decrypt and verify these messages.

Eskandarian believes a successful shared franking scheme should:

  • Safeguard the identity of the sender and the message contents
  • Make each message reportable
  • Protect users from being framed for messages they didn’t send
  • Ensure the moderator is the sole verifier for reported messages

Safeguarding the future

New online platforms offer many opportunities as well as fresh challenges. Since individuals interact with these platforms at younger and younger ages, Eskandarian also wants to educate the next generation about online safety.

Eskandarian teaches college courses in cryptography and privacy-enhancing technologies and has given several presentations on cryptography to high school students. He uses a cipher wheel to show how secret messages can be scrambled and unscrambled.

“Understanding why something is useful or important is one of the biggest ways to motivate someone to study that thing,” he says. “I think, at least I hope, that if I work on compelling problems, more people will be interested in learning about this.”

In June 2023, Eskandarian received a National Science Foundation CAREER Award for his research on improving the process of reporting abusive content and the development of educational materials on these topics.

“We value privacy, we value safety, and these things seem to be at odds,” he says. “I love these cases where there’s a hard puzzle and cryptography potentially offers a way to cut the Gordian knot.”

Read more about Saba Eskandarian’s research.