Kintsugi: Decentralized E2EE Key Recovery
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arXiv
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| Format: | Preprint |
| Published: |
2025
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| _version_ | 1866916867918004224 |
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| author | Ma, Emilie Kleppmann, Martin |
| author_facet | Ma, Emilie Kleppmann, Martin |
| contents | Kintsugi is a protocol for key recovery, allowing a user to regain access to end-to-end encrypted data after they have lost their device, but still have their (potentially low-entropy) password. Existing E2EE key recovery methods, such as those deployed by Signal and WhatsApp, centralize trust by relying on servers administered by a single provider. Kintsugi is decentralized, distributing trust over multiple recovery nodes, which could be servers run by independent parties, or end user devices in a peer-to-peer setting. To recover a user's keys, a threshold $t+1$ of recovery nodes must assist the user in decrypting a shared backup. Kintsugi is password-authenticated and protects against offline brute-force password guessing without requiring any specialized secure hardware. Kintsugi can tolerate up to $t$ honest-but-curious colluding recovery nodes, as well as $n - t - 1$ offline nodes, and operates safely in an asynchronous network model where messages can be arbitrarily delayed. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_21122 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Kintsugi: Decentralized E2EE Key Recovery Ma, Emilie Kleppmann, Martin Cryptography and Security Kintsugi is a protocol for key recovery, allowing a user to regain access to end-to-end encrypted data after they have lost their device, but still have their (potentially low-entropy) password. Existing E2EE key recovery methods, such as those deployed by Signal and WhatsApp, centralize trust by relying on servers administered by a single provider. Kintsugi is decentralized, distributing trust over multiple recovery nodes, which could be servers run by independent parties, or end user devices in a peer-to-peer setting. To recover a user's keys, a threshold $t+1$ of recovery nodes must assist the user in decrypting a shared backup. Kintsugi is password-authenticated and protects against offline brute-force password guessing without requiring any specialized secure hardware. Kintsugi can tolerate up to $t$ honest-but-curious colluding recovery nodes, as well as $n - t - 1$ offline nodes, and operates safely in an asynchronous network model where messages can be arbitrarily delayed. |
| title | Kintsugi: Decentralized E2EE Key Recovery |
| topic | Cryptography and Security |
| url | https://arxiv.org/abs/2507.21122 |