# MITM - user verification \[in person\]

**URL:** <https://forum.delta.chat/t/mitm-user-verification-in-person/5285>\
**Category:** Uncategorized\
**Tags:** security\
**Created:** [May 20, 2026, 2:57am UTC](https://forum.delta.chat/t/mitm-user-verification-in-person/5285 "2026-05-20T02:57:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![billy](https://forum.delta.chat/letter_avatar_proxy/v4/letter/b/ecd19e/32.png) [@billy](https://forum.delta.chat/u/billy)\
**Post date:** [May 20, 2026, 2:57am UTC](https://forum.delta.chat/t/mitm-user-verification-in-person/5285/1 "2026-05-20T02:57:58Z")

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Why do DC developers assume that everyone carries a phone all the time, for instance at a party?  
**Some of us don’t use phones at all.**

Why is there no simple and obvious solution to confirm that there is no man-in-the-middle attack?  
**How can we confirm the identity of a contact?**

Even in the ancient OTR (Off-the-Record) protocol, there was a simple authentication method (Socialist Millionaire’s Protocol).

Seriously, do we need to dig through settings to find the fingerprint (is it hidden on purpose?), and then must we install Signal or WhatsApp just to confirm the fingerprint?  
**Is this just a security/privacy cabaret for me?**

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**Author:** ![ian](https://forum.delta.chat/user_avatar/forum.delta.chat/ian/32/3164_2.png) [@ian](https://forum.delta.chat/u/ian)\
**Post date:** [May 20, 2026, 8:53am UTC](https://forum.delta.chat/t/mitm-user-verification-in-person/5285/2 "2026-05-20T08:53:25Z")

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Duplicate of:

> [@Sharing Delta Chat contact using voice or pen and paper](https://support.delta.chat/t/sharing-delta-chat-contact-using-voice-or-pen-and-paper/5125/2):
>
> TL;DR Print the invite QR and minimized i.delta.chat link on your business card or on a regular sheet of paper cut up to small slices. The recipient of such a card can either scan or type it in at home. No theoretical decentralized alternative could provide you a way to remember it and spell it out over the phone, because any such scheme would preferably require sharing at least 256 bits of entropy (43 random characters in base64 or 52 in more “easily” remembered base32). Even a toy scheme would…