Key Highlights
- Vitalik Buterin welcomed Signal’s plan to allow account registration without phone numbers, citing reduced telecom dependence and protection against SIM-swap risks.
- Buterin argued that pseudonymity is no longer sufficient in 2026, as AI can use metadata such as message timing, contact patterns, frequency, and size to reconstruct identities.
- He identified message-by-message unlinkability as the stronger long-term privacy standard, pointing to technologies such as mixnets and privacy-focused messengers as potential paths forward.
Ethereum co-founder Vitalik Buterin commented on recent developments from the encrypted messaging application Signal, which is working on allowing users to register accounts without a phone number.
In an X post on Friday, Buterin outlined both the benefits of this change and its limitations regarding privacy. He identified several advantages. First, it would reduce dependence on phone numbers. Beyond any privacy considerations, this lessens reliance on a concentrated system of control points in telecommunications.
Second, phone numbers often serve poorly as a foundation for identity in access control, given the frequency of SIM-swapping incidents.
Third, accounts free of phone numbers would complicate future efforts to restrict users by country of origin, thereby reducing the ability of governments to pressure the service into blocking their own citizens.
Buterin’s stance on pseudonymity
On privacy grounds, Buterin stated that the change represents an improvement over the current situation. However, he argued that pseudonymity has become obsolete in 2026. He pointed to numerous channels through which users unintentionally reveal information about themselves over time, including message timing, patterns of contacts, frequency, and message size.
He further noted the availability of effective AI-based methods, including large language models applied both to individual users and more broadly, that can reconstruct identities from such residual data.
Buterin observed that servers typically learn a user’s IP address. Even when this is masked through a VPN or Tor, other vectors of identity leakage remain. Consequently, he concluded that the only sustainable form of privacy is message-by-message unlinkability, in which no party other than the sender and receiver can determine the pairing of the two, and ideally neither party’s identity is known to outsiders.
The Crypto Times team tried to reach out to Signal for a comment on the matter, but it has not responded at the time of publication.
2×2 privacy taxonomy
Buterin explained a taxonomy of privacy outcomes arranged as a 2×2 grid. In the “sitting duck” case, an adversary knows both the actor and the action. Confidentiality, already provided by end-to-end encryption, leaves the adversary knowing the actor but not the content of the action. Anonymity, equivalent to message-by-message unlinkability, leaves the adversary knowing the action but not the actor. The ideal case leaves the adversary knowing neither.
He noted that Signal has long offered confidentiality. The removal of phone-number requirements would add a layer of pseudonymity, in which an adversary might initially see only an opaque identifier performing actions and later attempt to link that identifier to a real person.
The preferred state remains full message-by-message unlinkability. Achieving this, Buterin wrote, enters technical territory already under exploration by mixnet projects and by alternative messengers such as Session and SimpleX Chat.
Buterin analyzes expansion of AI capabilities
Buterin concluded by expressing the hope that the widespread adoption of end-to-end encryption is recognized as an achievement, that Signal proceeds with phone-number-free accounts, which he regarded as beneficial even without additional privacy gains, and that development continues toward minimizing data leakage.
This commentary follows earlier analysis by Buterin on the expansion of artificial intelligence capabilities and their implications for human society. In that prior framework he examined multi-dimensional abilities of both people and machines and explored forms of integration rather than simple replacement.
Buterin’s remarks frame Signal’s planned change as a practical improvement that addresses specific structural weaknesses of phone-number-based registration while falling short of the stronger privacy property he considers necessary. He positions message-by-message unlinkability as the relevant long-term objective and notes the technical and operational obstacles that remain, particularly around abuse prevention.
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