**Signal** is a mobile app developed by Signal Messenger LLC. The app provides instant messaging and calls secured with the Signal Protocol, an extremely secure encryption protocol which supports forward secrecy[^1] and post-compromise security.[^2]
3. Enter a username. Your username will always be paired with a unique set of digits to keep your username unique and prevent people from guessing it, for example if you enter "John" your username might end up being `@john.35`. By default, only 2 digits are paired with your username when you create it, but you can add more digits until you reach the username length limit (32 characters).
4. Go back to the main app settings page and select **Privacy**.
5. Select **Phone Number**
6. Change the **Who Can See My Number** setting to: **Nobody**
You can optionally change the **Who Can Find Me By Number** setting to **Nobody** as well, if you want to prevent people who already have your phone number from discovering your Signal account/username.
Contact lists on Signal are encrypted using your Signal PIN and the server does not have access to them. Personal profiles are also encrypted and only shared with contacts you chat with. Signal supports [private groups](https://signal.org/blog/signal-private-group-system), where the server has no record of your group memberships, group titles, group avatars, or group attributes. Signal has minimal metadata when [Sealed Sender](https://signal.org/blog/sealed-sender) is enabled. The sender address is encrypted along with the message body, and only the recipient address is visible to the server. Sealed Sender is only enabled for people in your contacts list, but can be enabled for all recipients with the increased risk of receiving spam.
The protocol was independently [audited](https://eprint.iacr.org/2016/1013.pdf) in 2016. The specification for the Signal protocol can be found in their [documentation](https://signal.org/docs).
If you use Android and your threat model requires protecting against [:material-target-account: Targeted Attacks](basics/common-threats.md#attacks-against-specific-individuals){ .pg-red } you may consider using this alternative app, which features a number of security and usability improvements, to access the Signal network.
**Molly** is an alternative Signal client for Android which allows you to encrypt the local database with a passphrase at rest, to have unused RAM data securely shredded, to route your connection via Tor, and [more](https://blog.privacyguides.org/2022/07/07/signal-configuration-and-hardening#privacy-and-security-features). It also has usability improvements including scheduled backups, automatic locking, and the ability to use your Android phone as a linked device instead of the primary device for a Signal account.
Molly is updated every two weeks to include the latest features and bug fixes from Signal. The exception is security issues, which are patched as soon as possible. That said, you should be aware that there might be a slight delay compared to upstream, which may affect actions such as [migrating from Signal to Molly](https://github.com/mollyim/mollyim-android/wiki/Migrating-From-Signal#migrating-from-signal).
Note that you are trusting multiple parties by using Molly, as you now need to trust the Signal team *and* the Molly team to deliver safe and timely updates.
There is a version of Molly called **Molly-FOSS** which removes proprietary code like the Google services used by both Signal and Molly, at the expense of some features like battery-saving push notifications via Google Play Services.
There is also a version called [**Molly-UP**](https://github.com/mollyim/mollyim-android#unifiedpush) which is based on Molly-FOSS and adds support for push notifications with [UnifiedPush](https://unifiedpush.org), an open source alternative to the push notifications provided by Google Play Services, but it requires running a separate program called [Mollysocket](https://github.com/mollyim/mollysocket) to function. Mollysocket can either be self-hosted on a separate computer or server (VPS), or alternatively a public Mollysocket instance can be used ([step-by-step tutorial, in German](https://kuketz-blog.de/messenger-wechsel-von-signal-zu-molly-unifiedpush-mollysocket-ntfy)).
Molly and Molly-FOSS support [reproducible builds](https://github.com/mollyim/mollyim-android/tree/main/reproducible-builds), meaning it's possible to confirm that the compiled APKs match the source code.
**SimpleX Chat** is an instant messenger that doesn't depend on any unique identifiers such as phone numbers or usernames. Its decentralized network makes SimpleX Chat an effective tool against [:material-close-outline: Censorship](basics/common-threats.md#avoiding-censorship){ .pg-blue-gray }.
SimpleX provides direct messaging, group chats, and E2EE calls secured with the [SimpleX Messaging Protocol](https://github.com/simplex-chat/simplexmq/blob/stable/protocol/simplex-messaging.md), which uses double ratchet encryption with quantum resistance. Additionally, SimpleX Chat provides metadata protection by using unidirectional ["simplex queues"](https://github.com/simplex-chat/simplexmq/blob/stable/protocol/simplex-messaging.md#simplex-queue) to deliver messages.
To participate in conversations on SimpleX Chat, you must scan a QR code or click an invite link. This allows you to verify a contact out-of-band, which protects against man-in-the-middle attacks by network providers. Your data can be exported and imported onto another device, as there are no central servers where this is backed up.
You can find a full list of the privacy and security [features](https://github.com/simplex-chat/simplex-chat#privacy-and-security-technical-details-and-limitations) implemented in SimpleX Chat on the app's repository.
SimpleX Chat was independently audited in [July 2024](https://simplex.chat/blog/20241014-simplex-network-v6-1-security-review-better-calls-user-experience.html#simplex-cryptographic-design-review-by-trail-of-bits) and in [October 2022](https://simplex.chat/blog/20221108-simplex-chat-v4.2-security-audit-new-website).
**Briar** is an encrypted instant messenger that [connects](https://briarproject.org/how-it-works) to other clients using the Tor Network, making it an effective tool at circumventing [:material-close-outline: Censorship](basics/common-threats.md#avoiding-censorship){ .pg-blue-gray }. Briar can also connect via Wi-Fi or Bluetooth when in local proximity. Briar’s local mesh mode can be useful when internet availability is a problem.
To add a contact on Briar, you must both add each other first. You can either exchange `briar://` links or scan a contact’s QR code if they are nearby.
The client software was independently [audited](https://briarproject.org/news/2017-beta-released-security-audit), and the anonymous routing protocol uses the Tor network which has also been audited.
Briar supports forward secrecy[^1] by using the Bramble [Handshake](https://code.briarproject.org/briar/briar-spec/blob/master/protocols/BHP.md) and [Transport](https://code.briarproject.org/briar/briar-spec/blob/master/protocols/BTP.md) protocol.
These messengers do not have forward secrecy[^1], and while they fulfill certain needs that our previous recommendations may not, we do not recommend them for long-term or sensitive communications. Any key compromise among message recipients would affect the confidentiality of **all** past communications.
**Element** is the flagship client for the [Matrix](https://matrix.org/docs/chat_basics/matrix-for-im) protocol, an [open standard](https://spec.matrix.org/latest) for secure decentralized real-time communication.
With the integration of [Element Call](https://element.io/blog/we-have-lift-off-element-x-call-and-server-suite-are-ready) into Element's web app, desktop apps, and its [rewritten mobile apps](https://element.io/blog/element-x-experience-the-future-of-element), group VoIP and video calls are E2EE by default.
The Matrix protocol itself [theoretically supports forward secrecy](https://gitlab.matrix.org/matrix-org/olm/blob/master/docs/megolm.md#partial-forward-secrecy)[^1], however this is [not currently supported in Element](https://github.com/vector-im/element-web/issues/7101) due to it breaking some aspects of the user experience such as key backups and shared message history.
The protocol was independently [audited](https://matrix.org/blog/2016/11/21/matrixs-olm-end-to-end-encryption-security-assessment-released-and-implemented-cross-platform-on-riot-at-last) in 2016. The specification for the Matrix protocol can be found in their [documentation](https://spec.matrix.org/latest). The [Olm cryptographic ratchet](https://matrix.org/docs/matrix-concepts/end-to-end-encryption) used by Matrix is an implementation of Signal’s [Double Ratchet algorithm](https://signal.org/docs/specifications/doubleratchet).
**Session** is a decentralized messenger with a focus on private, secure, and anonymous communications. Session offers support for direct messages, group chats, and voice calls.
Session uses the decentralized [Oxen Service Node Network](https://oxen.io) to store and route messages. Every encrypted message is routed through three nodes in the Oxen Service Node Network, making it virtually impossible for the nodes to compile meaningful information on those using the network.
Session allows for E2EE in one-on-one chats or closed groups which allow for up to 100 members. It is also possible to [set up](https://docs.oxen.io/oxen-docs/products-built-on-oxen/session/guides/open-group-setup) or join open groups which can host thousands of members, but messages in these open groups are **not** end-to-end encrypted between participants.
Session was previously based on Signal Protocol before replacing it with their own in December 2020. Session Protocol does [not](https://getsession.org/blog/session-protocol-technical-information) support forward secrecy.[^1]
**Please note we are not affiliated with any of the projects we recommend.** In addition to [our standard criteria](about/criteria.md), we have developed a clear set of requirements to allow us to provide objective recommendations. We suggest you familiarize yourself with this list before choosing to use a project, and conduct your own research to ensure it's the right choice for you.
Our best-case criteria represents what we would like to see from the perfect project in this category. Our recommendations may not include any or all of this functionality, but those which do may rank higher than others on this page.
[^1]: [Forward secrecy](https://en.wikipedia.org/wiki/Forward_secrecy) is where keys are rotated very frequently, so that if the current encryption key is compromised, it does not expose **past** messages as well.
[^2]: Future Secrecy (or Post-Compromise Security) is a feature where an attacker is prevented from decrypting **future** messages after compromising a private key, unless they compromise more session keys in the future as well. This effectively forces the attacker to intercept all communication between parties, since they lose access as soon as a key exchange occurs that is not intercepted.
