--- id: CP-201 slug: zero-knowledge-password-manager lang: en title: Zero-Knowledge password managers description: How a password manager encrypts your vault from the master password, and what you do so that it really protects your accounts. canonical_url: https://startbrain.io/cyberpedia/en/articles/zero-knowledge-password-manager/ markdown_url: https://startbrain.io/cyberpedia/en/articles/zero-knowledge-password-manager.md publisher: Brain (https://startbrain.io) license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) cite_as: Brain, "Zero-Knowledge password managers", Cyberpedia, 2026. https://startbrain.io/cyberpedia/en/articles/zero-knowledge-password-manager/ (CC BY 4.0) wing: 3 theme: control_access reflex: cr-013 schema: G3 updated: "2026-11-03" translations: en: https://startbrain.io/cyberpedia/en/articles/zero-knowledge-password-manager/ fr: https://startbrain.io/cyberpedia/fr/articles/gestionnaire-mots-de-passe-zero-knowledge/ es: https://startbrain.io/cyberpedia/es/articles/gestor-contrasenas-zero-knowledge/ sources: - "n": 1 title: Password manager buyers guide publisher: NCSC (UK) url: https://www.ncsc.gov.uk/collection/passwords/password-manager-buyers-guide accessed: "2026-11-03" - "n": 2 title: "SP 800-132, Recommendation for Password-Based Key Derivation: Part 1: Storage Applications | CSRC" publisher: NIST url: https://csrc.nist.gov/pubs/sp/800/132/final accessed: "2026-11-03" - "n": 3 title: Password Storage - OWASP Cheat Sheet Series publisher: OWASP url: https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html accessed: "2026-11-03" - "n": 4 title: Les conseils de la CNIL pour un bon mot de passe publisher: CNIL url: https://www.cnil.fr/fr/les-conseils-de-la-cnil-pour-un-bon-mot-de-passe published: "2017-01-26" accessed: "2026-11-03" - "n": 5 title: Use Strong Passwords | CISA publisher: CISA url: https://www.cisa.gov/secure-our-world/use-strong-passwords accessed: "2026-11-03" - "n": 6 title: Three random words publisher: NCSC (UK) url: https://www.ncsc.gov.uk/collection/top-tips-for-staying-secure-online/three-random-words published: "2021-12-21" accessed: "2026-11-03" - "n": 7 title: Authentication - OWASP Cheat Sheet Series publisher: OWASP url: https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html accessed: "2026-11-03" - "n": 8 title: NIST Special Publication 800-63B publisher: NIST url: https://pages.nist.gov/800-63-3/sp800-63b.html accessed: "2026-11-03" - "n": 9 title: Pourquoi et comment bien gérer ses mots de passe ? - Assistance aux victimes de cybermalveillance publisher: Cybermalveillance.gouv.fr url: https://www.cybermalveillance.gouv.fr/tous-nos-contenus/bonnes-pratiques/mots-de-passe published: "2019-11-23" accessed: "2026-11-03" - "n": 10 title: "Credentials from Password Stores: Password Managers, Sub-technique T1555.005 - Enterprise | MITRE ATT&CK®" publisher: MITRE ATT&CK url: https://attack.mitre.org/techniques/T1555/005/ accessed: "2026-11-03" --- # Zero-Knowledge password managers A password manager keeps an employee's credentials in a vault. The vault opens with a single secret, the master password [1]. The dozens of passwords each person uses are hard to remember, and people reuse the same ones or choose common passwords, which attackers exploit [1]. In the ideal case described by the NCSC, the key that decrypts the vault is generally derived from the master password, and it should not be accessible to the provider of the synchronisation service [1]. This property has a downside: if the decryption key is lost, it must not be possible to reset it in order to recover the contents of the vault [1]. ## In 30 seconds - Where it happens: every time a password is created, typed or saved, at work as at home. - What the attacker wants: the master password or the plaintext credentials extracted from memory [10], because a successful attack gives access to all the stored passwords [1]. - The reflex: choose a long, unique passphrase as the master password [5][6], turn on multifactor authentication on the manager [1] and never reuse that secret elsewhere [4]. - If it's already done: find out whether a recovery option exists, who can trigger it, and whether you want it [1]. ## Straight answers ### Can the provider read my passwords? The NCSC (UK) guide describes the ideal case: the stored credentials are accessible only to the user, with their decryption key, generally derived from the master password. This key must not be accessible to others, the provider included [1]. A manager that offers recovery by the provider departs from this case: the NCSC warns that the recovery method can be exploited to gain access to the credentials, especially when the provider is responsible for it [1]. ### What happens if I forget the master password? You lose access to all your saved passwords and must reset the affected accounts one by one, which takes a lot of time [1]. Some managers offer a recovery that involves other authorised people: a colleague, an administrator or the provider [1]. The NCSC recommends deciding whether you want this option by weighing its risks against the cost of a lost vault [1]. ### Why isn't the master password used as is as the key? A key derivation function turns the password into an encryption key. In December 2010 NIST published recommendation SP 800-132, which describes the derivation of master keys from passwords or passphrases to protect stored data [2]. NIST states in 2023 that it plans to revise this document [2]. ### Can a password manager be attacked? Yes. The NCSC points out that, like any software, a manager can have vulnerabilities, and that it is a natural target since a successful attack gives access to all of a user's passwords [1]. The same guide concludes that the benefits outweigh the risks [1]. ## How it works The master password goes through a derivation function to produce the encryption key [2]. For storing passwords on the server side, OWASP recommends slow algorithms such as Argon2id, bcrypt or PBKDF2, and judges fast algorithms such as SHA-256 unsuitable, because they let the attacker test a very large number of combinations per second [3]. A slow algorithm that uses a lot of memory makes brute force harder, more costly and longer [3]. The tuning is done through a work factor, that is, the number of iterations of the algorithm for each password [3]. OWASP gives several equivalent minimum configurations for Argon2id, one of which is 19 MiB of memory, 2 iterations and a parallelism degree of 1, and, for PBKDF2 with a FIPS-140 requirement, a factor of 600,000 or more with HMAC-SHA-256 [3]. These figures describe server-side password storage. The sources in the file do not say which parameters each manager uses for its vault. On the usage side, the manager also fills in forms. It must offer the credentials only for the site where they were saved, never the whole vault to a visited site [1]. The NCSC adds that a manager can spot fake sites better than a human can [1]. ## What you do Choose a long passphrase as your master password. CISA suggests a string of 4 to 7 unrelated words [5]. The NCSC advises three random words, for example "applenemobiro", and advises against birth dates, sports teams, and the names of relatives or pets, which social media often reveals [6]. Replacing an "o" with a zero adds little strength, because cybercriminals know the trick [6]. The CNIL gives as an example a password of at least 12 characters of 4 types, and notes that it can be shorter if the account has additional safeguards [4]. Never reuse this master password. The CNIL asks for a password specific and unique to each sensitive account, in order to avoid cascading compromises [4]. Turn on multifactor authentication on the manager. With it, the attacker must know the master password and hold the second factor [1]. The NCSC asks for it to be used on all managers with cloud synchronisation, and for privileged accounts such as administrator accounts [1]. OWASP cites a Microsoft analysis according to which multifactor authentication would have stopped 99.9% of account compromises [7]. Decide whether you want a recovery method, by weighing its risks against the cost of a lost vault, and know who could trigger it [1]. If your company has a policy, follow it. The NCSC recommends that the organisation (system owners) define a clear policy on exporting the vault in plaintext, because once exported, the passwords are no longer protected [1]. Let the manager generate the passwords for your other accounts: it makes it easier to use unique, long and random passwords [1]. NIST notes that pasting into input fields makes managers easier to use [8]. This version of NIST SP 800-63 has been replaced by SP 800-63-4 since 1 August 2025 [8]. ## Pitfalls - A weak master password. The attacker can try to guess it by brute force [10]. For the master password policy, MITRE refers to NIST recommendations [10]. - Phishing. MITRE advises training users to recognise phishing attempts that steal session cookies or credentials [10]. - The vault open in memory. Once the database is unlocked, the credentials can be copied in memory, and attackers extract the master password or the plaintext credentials from it [10]. MITRE advises locking the manager again after a short delay [10]. - Outdated software. MITRE recommends regularly updating browsers, managers and related software [10], and the NCSC recommends checking that the vendor fixes its flaws quickly [1]. - Extensions and the browser. The manager often relies on a browser extension to fill in forms [1]. MITRE lists the data of browser extensions and managers among the targets of some malware [10]. On a shared computer, Cybermalveillance.gouv.fr advises against saving passwords in the browser [9]. - Stolen vault databases. MITRE cites actors and malware that have targeted these databases: Threat Group-3390 obtained a KeePass database on a compromised machine, and Indrik Spider exported passwords from managers [10]. - Losing the secret without recovery. If the key is lost and no recovery exists, the vault stays unreadable [1]. - Plaintext notes. Sticky notes, text files, messaging or phones are not designed to store passwords [4]. ## Sources 1. NCSC (UK), "Password manager buyers guide". https://www.ncsc.gov.uk/collection/passwords/password-manager-buyers-guide (accessed 3 November 2026) 2. NIST, "SP 800-132, Recommendation for Password-Based Key Derivation: Part 1: Storage Applications | CSRC". https://csrc.nist.gov/pubs/sp/800/132/final (accessed 3 November 2026) 3. OWASP, "Password Storage - OWASP Cheat Sheet Series". https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html (accessed 3 November 2026) 4. CNIL, "Les conseils de la CNIL pour un bon mot de passe", 26 January 2017. https://www.cnil.fr/fr/les-conseils-de-la-cnil-pour-un-bon-mot-de-passe (accessed 3 November 2026) 5. CISA, "Use Strong Passwords | CISA". https://www.cisa.gov/secure-our-world/use-strong-passwords (accessed 3 November 2026) 6. NCSC (UK), "Three random words", 21 December 2021. https://www.ncsc.gov.uk/collection/top-tips-for-staying-secure-online/three-random-words (accessed 3 November 2026) 7. OWASP, "Authentication - OWASP Cheat Sheet Series". https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html (accessed 3 November 2026) 8. NIST, "NIST Special Publication 800-63B". https://pages.nist.gov/800-63-3/sp800-63b.html (accessed 3 November 2026) 9. Cybermalveillance.gouv.fr, "Pourquoi et comment bien gérer ses mots de passe ? - Assistance aux victimes de cybermalveillance", 23 November 2019. https://www.cybermalveillance.gouv.fr/tous-nos-contenus/bonnes-pratiques/mots-de-passe (accessed 3 November 2026) 10. MITRE ATT&CK, "Credentials from Password Stores: Password Managers, Sub-technique T1555.005 - Enterprise | MITRE ATT&CK®". https://attack.mitre.org/techniques/T1555/005/ (accessed 3 November 2026) --- Original source: Cyberpedia, the public cybersecurity and AI encyclopedia published by Brain. 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