The sensitive messenger

Decentralized instant messenger


Newest version



Security notices

Running on tablets

History of changes




Source code

Newest version

Download (HTTP for older browser compatibility) version released on 03.11.2021. This requires at least Windows 7 SP1. For an operating system before Windows 10, if you aren't current with all the updates, you might have to first install Microsoft's .Net 4.8 from here.

If you are an existing user, also see the security notices.

The source code (with which the application was built) is included in the downloaded archive.

See this for how to run the program.

It's strongly recommended to read the QA before you use the program.

Main window screenshot


Vela is a mix between an instant messenger and an email manager applications.

Vela combines the communication speed of instant messages with the storage features of emails, and adds digital signatures, encryption, reliability of delivery and lack of spam.

Vela has no centralized authentication service. The authentication is achieved with UPNs. A UPN (= Universal Peer Name) is a text made of a few tens of random-looking characters. UPNs are shared by the users like email addresses.

A key feature of Vela is that messages can be transferred offline from peer to peer (that is, even when their computers are not connected to the Internet), by exporting and importing them.

If you want to know Vela's advantages over encrypted email, see this.

Continuing the tradition started with PicturePuzzle and Wallperizer of doing something interesting with images, Vela lets you (remotely) change the wallpaper of your close friends, and even to write text on it. If you want to share images, wish happy holidays or even make a love declaration, see how to send a wallpaper.


Attesting document

The attesting document of the Vela archive is this.

To verify the authenticity of the Vela archive, download the attesting document and use the "Root-verify attesting document" button from the "General" tab of Vela. This, of course, assumes that you already have a version of Vela that you can trust. This method can be used to verify application updates.

You can use the same attesting document to verify the authenticity using version 1.0.0 or 1.0.1.

This method is authoritative but it requires that you already use a trusted version of Vela. The security of this method doesn't depend on the security of this website.


The SHA-512 of the Vela archive is 5A3B-CA7D-51E5-A1B0-E716-B115-1DCC-9B3D-88F8-0B77-FD78-0F58-55A5-96C8-D0CE-7395-184A-6A9E-15F9-5E28-41AF-23F7-EC36-4EF6-7C9E-E8F9-36A4-DF55-CC64-9820-1566-283F.

The SHA-256 of the Vela archive is F67E-7A0F-7B17-ED2E-311F-07D2-10E9-B1E3-F3CA-AFE6-D3DD-42D6-A277-40EB-CF04-4873.

The security of this method depends on the security of this website, specifically on the accuracy of the hashes shown here.

Online timestamp

Download this file and then drag-and-drop it together with the Vela archive on this webpage in order to verify the authenticity assured by the timestamp service.

The authenticated time (in GMT format) is 2021-11-03 23:37:34.

The security of this method depends on the security of this website, specifically on the accuracy of the time shown here.

Security notices

Please update to the newest version of Vela.

Versions 1.0.0 through 1.4.3

The side-channel timing attack protection had a bug.

Versions 1.0.2 through

If you have created vaults with these versions of Vela after you have reopened the storehouse in which they are stored, and you've used a simple password for it, it's recommended to create new vaults instead of those, if you have reasons to believe that you may be the target of a highly resourceful attacker who can retrieve information from your computer.

Versions 1.0.0 through 1.0.1

If you have created your storehouse / vault with these versions of Vela, it's recommended to create a new storehouse / vault, if you have reasons to believe that you may be the target of a highly resourceful attacker who can retrieve information from your computer.

Running on tablets

It's possible to run the program on tablets which have full Windows.

However, by default, Windows on tablets uses a sleep mode called "connected standby", mode which once active stops all desktop applications (but not the ModernUI ones).

Because of this, network downloads stop, instant messengers don't receive messages, email clients don't check for new mail, sound stops, and so on.

In this mode, if the tablet's display is turned off, the connected standby mode is activated, that is, there is no separation between the display and the sleep mode.

In order to deactivate the connected standby and keep the desktop applications running when the display turns off, you have change something in the tablet's registry.

Go to the "HKEY_LOCAL_MACHINE \ System \ CurrentControlSet \ Control \ Power \ CSEnabled" key and set its value to 0 (from its default value of 1). Then restart the computer. Then, in the current power plan set the time after which the display is turned off.

Note that once the connected standby mode is deactivated, the tablet can no longer sleep, though it can hibernate, so even if the display is turned off, the tablet will consume a lot more energy than with the connected standby mode active.

History of changes

Version, 03.11.2021

Improvement: Deterministic build.

Improvement: Upgrade to .Net 4.8.

Small bug fixes.

Version, 24.12.2016

Feature: Added account aliases to minimize the risk of sending letters to the wrong contacts. In the "User interface" tab of the "Application Configuration" window, check the "Letters may be sent only if they are prefixed with an account alias" check-box. Also, modify the account alias for every account that you have.

Feature: Added the ability to run command lines on the computers of trusting peers. In the "Edit Account" window, see the "Remote access" tab.

Improvement: Letters can be exported in an obfuscated form (to look like random data), like when they are sent online, by using a non standard extension for the saved file. Note that while spies can only see random data, anyone who has the UPN of the recipient can see that the data contains a letter (though its message remains hidden). The size of the saved file may vary with up to 64 KiB, to hinder statistical analysis as much as possible. The recipients of such letters must have a version of Vela which supports this feature.

Improvement: Dramatically improved the layout of the list of letters.

Improvement: Emoticons and image previews are always displayed below the letter summary.

Improvement: Up to 3 image previews can be displayed for each letter.

Improvement: Emoticons may be either thumb-sized or full-sized.

Improvement: Image previews are always full-sized.

Improvement: Double-click an image preview to open the image file in the default image viewer application.

Improvement: The retry schedule for sending requests to the remote peers is continuously randomized.

New emoticons: Added 21 emoticons.

Bug workaround: A .Net bug causes parts of code which are compiled for 64-bit to run much slower than when compiled for 32-bit. The workaround has increased the file transfer speed, for the reference setup, from 9 MB / s to 13 MB / s. When Microsoft will fix this bug, the speed will increase a bit more.

Bug fixes.


Bug fix: Vela would freeze when trying to send / receive messages with some odd combinations of line breaks (because the removal of multiple consecutive line breaks would enter into an infinite loop).


Improvement: Added the "Filler UPN classifiers count" edit-box in the "Advanced" tab of the "Application Configuration" window, to edit the number of UPN classifiers which are registered on the peer network, as filler peer names.

Improvement: When verifying a signature, the signing time is shown.

Improvement: Added RSA blinding to protect against acoustic cryptanalysis.

There is a security notice for previous versions.

Small changes.

Technical explanation:

  • The filler UPN classifiers are used strictly to create a larger peer network because the PNRP has problems resolving remote peer names when just one local peer name is registered. If the PNRP still can't find peers, increase this value; it's useful if the remote peers also increase this value.

  • Because the filler classifiers have the same size and structure as normal UPN classifiers, and because a fixed number of them is registered on the network, an attacker can't know how many vaults a peer has. However, if the peer creates a new vault, the attacker will see a change in the registered classifiers.


Improvement: The handling of the letter flags has been revamped to allow easier navigation and updating.

Improvement: Added an edit-box in the "Advanced" tab of the "Application Configuration" window to edit the size of the cache which is used for sending and receiving data through the network, for large data transfers.

Improvement: Added the "Retry send" menu in the context menu of the list of letters, to retry to send the focused letter as soon as possible.

Improvement: The letters which are copied to the clipboard are numbered.

Improvement: The notification window which is displayed in the top-right corner of the main window is hidden when the application is minimized or hidden.

Improvement: The "Retry" state of accounts has a small orange rectangle as prefix, just like the "Retry" state of letters has. The "Next time" value is also updated every time the tooltip is opened, just like it happens for letters.

Improvement: The details of pending accounts can be viewed by entering in "edit" mode.


Improvement: When a letter which contains the ";Bell", ";Horn" or ";Urgent" emoticon symbol is received, a desktop notification is shown in the bottom-right corner of the screen (until it's clicked).

Improvement: It is periodically checked (and shown) if a "New letter" notification exists but the application's button is not shown in the system's taskbar.

Bug fix: It was possible for "New letter" notifications to not be shown, due to optimizations made by the infrastructure.


Improvement: The maximum possible file transfer speed has increased with about 60%. Due to network conditions, this improvement will benefit mostly file transfers over the local area network.

Bug fix: If a vault was deleted, all the accounts were deleted.

Bug fix: If several accounts referring to the same remote peer existed in a storehouse, if one of them was deleted then letters were no longer received and the accounts were no longer loaded until they were manually recreated.

In order to benefit from the file transfer speed improvement, you and your contacts must use at least version 1.4 of Vela. In the case of very fast networks, in order to achieve the entire potential of the improvement, you and your contacts must use accounts created using (the UPNs of) vaults generated with at least version 1.4 of Vela.

If you generate a vault with at least version 1.4 of Vela and you send its UPN to some people, you can communicate with those people only if they also have at least version 1.4 of Vela.

Tests have shown that, for a 1 Gbps wired local area network, the transfer speed (for large files) is 8...12 MB / s.

Technical explanation:

  • The socket communication buffer size is much higher for file transfers.

  • Action requests are encrypted once with the recipient's public identity, and once during frame obfuscation with the encryption key of the recipient's UPN. However, an action response was until now once encrypted with the encryption key from the request, and once during frame obfuscation with the same key, which means that the first encryption layer is redundant. By removing the first encryption layer (only for file transfers), the file transfer speed is increased without compromising the security.


Improvement: Improved file transfer state on the sender's side. The sender now sees either a transferred or error state. If the "√" character is shown before the number of files, it's certain that the files have been fully transferred.

Bug fix: The resolution of the alternative peer addresses was performed (in some cases) only if the "Use UPN resolvers" was checked (in the "General" tab of the "Application Configuration" window).


New emoticons: ";Elephant" (in the "Main" tab), ";Karate" (in the "Secondary" tab).

Improvement: The names of the files attached to a letter are validated when the files are attached, not only during transfer. This will catch errors before the letter is sent.

Improvement: The names of the files attached to letters are not written on the sent wallpapers.

Bug fix: Showing images attached to letters was wasting huge amounts of working memory. The underlying UI framework is still wasting a lot of working memory while handling images.

Small changes.


Improvement: Switched to .Net 4.5 in order to support partial item scroll in the list of letters.

Improvement: When files are attached to the draft letter, a file or folder name is appended to the draft letter text-box.

Improvement: Better estimation of the PNRP status.

Improvement: Offers to download files from yellow contacts are no longer accepted, for safety reasons.

Bug fix: Reloading many times a large number of custom emoticons was causing the application to crash.

Bug fix: When Vela was started together with the operating system, the list of letters was not automatically scrolled to the bottom.

Small changes.


Bug fix: An error was occurring when a storehouse was being closed after a letter was created.


Bug fix: The download progress state of a letter is changed to "Pending" after the download is resumed after an interruption (when the state contained an error).

Bug fix: The "Next time" of the download progress of a letter is shown.

Small changes.

There is a security notice for previous versions.


Improvement: The "Select emoticon" window remembers its size, position and last viewed category.

Small changes.


Improvement: To remove a "New letter" notification, you can no longer click outside the draft letter text-box; users could have easily missed notifications by scrolling the list of letters because they were focusing on the list.

Small changes.


Improvement: Pressing the "Ctrl + E" key in the "Select Emoticon" window updates the emoticons with the custom ones.

Improvement: Added a confirmation query for the "Update emoticons" menu from the context menu of the list of letters.

Improvement: Better updating performance when custom emoticons are received in a letter.

Bug fix: When multiple emoticon images where shown below a letter's summary, the images were not clear.

Bug fix: The PNRP was started (but no UPNs were registered) even when the peer was offline.

Small changes.


Improvement: Added the "Attach custom emoticons" menu to the context menu of the draft letter text-box (from the "Letters" tab), menu which attaches the (local peer's) custom emoticons to the draft letter.

Improvement: Added buttons (in the "Application" tab) to explore the application's configuration and temporary folders.

Bug fix: Some edit-boxes which may be empty were requiring text.


Feature: Added support for custom emoticons.

New emoticons: ";NoTalk" (in the "Main" tab), ";Emoticons" (in the "Secondary" tab).

Improvement: Better organization for the emoticons, and better user interaction with the emoticon category buttons.

Improvement: Partial frames for animated images are supported.

Improvement: When a newer page from the list of letters is shown, the list is scrolled to the top, not to the bottom, in order to preserve the continuity of reading while switching the current page back and forth.

Small changes.


Improvement: Added a workaround for a .Net bug where an image which is retrieved from the clipboard is saved blank / garbled, if it was first processed in another application.

Improvement: The summary of the letters (from the list of letters) which have no image preview extend to the margin of the list.

Improvement: The transient letters are deleted even when the operating system is closing, at least if it waits for the application enough time.

Improvement: Better contrast for some emoticon images, and added several emoticon symbols (mainly for the kind which start with ":").

Small changes.


New emoticons: ";AngelLaugh", ";AngelLol", ";AngelSmile", ";AngelSurprised", ";AngelTired", ";AngelUpset", ";Cottage", ";Countryside", ";Fireworks", ";Hopeless", ";Treasure", all in the "Secondary" tab.

Improvement: Better detection when a "New letter" notification has to be removed after the application's main window is focused.

Improvement: When the "Alternative peer address" or "Overridden remote port" is changed in the "Edit Account" window, the letters are sent as soon as possible to the remote peer.

Improvement: When the application is started for the first time, a message window lets the user to either create or open a storehouse. This is useful when the user reinstalls the operating system.

Small changes.


Improvement: Better detection of the moment when a peer comes online after a long period of being offline.

Improvement: Multiple consecutive line breaks are reduced to a single one in a letter's summary.

Improvement: Added a button in the "Application" tab which opens a command line window with the PNRP state.


Improvement: The summary of the letters (from the list of letters) is colored differently for the sender and for the recipient.

Improvement: The list of letters is scrolled a single item at a time when the mouse wheel is rotated.

Improvement: When the flag filter or the page is changed in the "Letters" tab, the list of letters is scrolled to the bottom.

Bug fix: Double-clicking on the scrollbar from the list of letters was opening a letter (in a separate window).

Bug fix: Letter import was failing.


Improvement: When many files are attached, it's not checked that all of them can be read, which makes the attaching much faster.

Improvement: A more descriptive error is shown when a UPN / alternative peer address can't be resolved.

Bug fix: When an empty file was among some files to attach, no file was attached; the empty files are not attached anymore.

Small changes.


Improvement: It's possible to send the draft letter (from the "Letters" tab) by pressing the "Enter" key rather than "Ctrl + Enter"; see the "User interface" tab of the "Application Configuration" window for options.

Improvement: If an error occurs while trying to open a storehouse, the user is automatically prompted to type the password (again).

Improvement: The design of the list of letters is slightly more compact.

Improvement: When a letter contains an emoticon symbol, its "No preview" / speaker image preview is not shown, but the emoticon thumbnail is shown instead.

Bug fix: Sometimes the application would crash, especially immediately after sending a letter.

Small changes.


Bug fix: The image preview of an attached image file was not being shown when an emoticon symbol was included in the letter.

Small changes.


Bug fix: The image preview of a received letter was not being shown if the file transfer took more than a fraction of a second.


Feature: Expanded the support for animated images.

Feature: The emoticon column from the list of letters shows a preview of an image attached to each letter, if one is available, instead of the letter's emoticon thumbnail image. Animated images are being animated.

Feature: If a letter's summary (= the message part shown in the list of letters) contains several emoticon symbols, the associated images are displayed below the summary.

New emoticon: ";Freezing" (in the "Secondary" tab).

Improvement: Added symbols for existing popular emoticons (from other messaging applications).

Improvement: It's possible to show / hide the "State time" column from the list of letters.

Improvement: It's possible to show / hide the horizontal separator between the letters from the list of letters.

Improvement: It's possible to show / hide the full-sized emoticon image from the "Letters" tab.

Improvement: It's possible to horizontally shrink the main window a lot more, but you should first hide the "State time" column and the full-sized emoticon image from the list of letters.

Improvement: Middle-click on a letter from the list of letters is a shortcut for "Reply".

Improvement: It's possible to explore the attached files for sent letters.

Improvement: A single application instance can be started.

Bug fix: The "Visit URL" feature was failing to detect URLs in some conditions.

Bug fix: Pressing the "Ctrl + V" key in the message text-box (in the "Letters" tab) failed to paste texts.

Small changes.


Feature: Added tooltip for the emoticon thumbnail column (from the letter list), which shows the full-sized preview of an image file attached to the letter (if that exists), or the full-sized emoticon.

Feature: The image from the clipboard can be pasted into the message text-box (in the "Letters" tab) in order to attach it as a file.

Improvement: The text to write on wallpaper has no more lower size limit, that is, any text (excluding the ";Paradise" emoticon) will be written.

Improvement: When attaching files, they are checked to see if they can be read.

Improvement: The recipient of a letter sees a clear error message when a file attached to the letter is being used (by another application) and can't be downloaded.

Improvement: To remove a "New letter" notification, you can now also hide (not minimize) the application's main window.

Improvement: Pressing the "Ctrl + C" key copies to the clipboard the text selected in the focused letter (from the letters list).

Improvement: The time of the next retry is dynamically updated (in the letter state tooltip).

Bug fix: Image files were not being shown in the selection window for a vault's photo.

Bug fix: A trivial error was occurring when files were being downloaded and the letter didn't have the ";Paradise" emoticon.

Small changes.


Feature: Write text on sent wallpapers.

Improvement: The ";Paradise" emoticon is required to send a wallpaper.

New emoticon: ";Paradise" (in the "Secondary" tab).

Small changes.


Feature: Send wallpapers.

Feature: You can play the media files attached to a letter.

Feature: You can view the names of the files attached to a received letter by using the "View attached files names" menu from the context menu of a letter.

New emoticon: ";Wizard" (in the "Secondary" tab).

Small changes.


Changed the root presenter to RSA 8192.

Bug fix: The displayed file transfer progress was limited to 1 (instead of 100).

Small changes.

There is a security notice for previous versions.


Public release of Vela version 1.

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