VeraCrypt/doc/html/Trim Operation.html

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<h1>Trim Operation</h1>
<div style="text-align:left; margin-top:19px; margin-bottom:19px; padding-top:0px; padding-bottom:0px">
Some storage devices (e.g., some solid-state drives, including USB flash drives) use so-called 'trim' operation to mark drive sectors as free e.g. when a file is deleted. Consequently, such sectors may contain unencrypted zeroes or other undefined data (unencrypted)
 even if they are located within a part of the drive that is encrypted by VeraCrypt.<br>
<br>
On Windows, VeraCrypt allows users to control the trim operation for both non-system and system volumes:
<ul>
<li>For non-system volumes, trim is blocked by default. Users can enable trim through VeraCrypt's interface by navigating to "Settings -> Performance/Driver Configuration" and checking the option "Allow TRIM command for non-system SSD partition/drive."</li>
<li>For <a href="System%20Encryption.html">system encryption</a>, trim is enabled by default (unless a <a href="Hidden%20Operating%20System.html">hidden operating system</a> is running). Users can disable trim by navigating to "System -> Settings" and checking the option "Block TRIM command on system partition/drive."</li>
</ul>

Under Linux, VeraCrypt does not block the trim operation on volumes using the native Linux kernel cryptographic services, which is the default setting. To block TRIM on Linux, users should either enable the "do not use kernel cryptographic services" option in VeraCrypt's Preferences (applicable only to volumes mounted afterward) or use the <code>--mount-options=nokernelcrypto</code> switch in the command line when mounting.
<br>
<br>
Under macOS, VeraCrypt does not support the trim operation. Therefore, trim is always blocked on all volumes.
<br>
<br>
In cases where trim operations occur, the adversary will be able to tell which sectors contain free space (and may be able to use this information for
 further analysis and attacks) and <a href="Plausible%20Deniability.html" style="text-align:left; color:#0080c0; text-decoration:none.html">
plausible deniability</a> may be negatively affected. In order to avoid these issues, users should either disable trim in VeraCrypt settings as previously described or make sure VeraCrypt volumes are not located on drives that use the trim operation.</div>
<p>To find out whether a device uses the trim operation, please refer to documentation supplied with the device or contact the vendor/manufacturer.</p>
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Add HTML documentation. 2017-05-13 17:34:16 +02:00			`<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"`
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			`<title>VeraCrypt - Free Open source disk encryption with strong security for the Paranoid</title>`
			`<meta name="description" content="VeraCrypt is free open-source disk encryption software for Windows, Mac OS X and Linux. In case an attacker forces you to reveal the password, VeraCrypt provides plausible deniability. In contrast to file encryption, data encryption performed by VeraCrypt is real-time (on-the-fly), automatic, transparent, needs very little memory, and does not involve temporary unencrypted files."/>`
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Minor cleanup of the repo (#822) * : source files should not be executable : make sure files have final newline : remove BOM from text files translations: unify headers * : fix typos *: trim excess whitespace 2021-09-04 21:59:25 +02:00			`<div>`
Increment version to 1.25-RC2 and update release notes 2021-11-21 20:03:27 +01:00			`<a href="Documentation.html"><img src="VeraCrypt128x128.png" alt="VeraCrypt"/></a>`
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Minor cleanup of the repo (#822) * : source files should not be executable : make sure files have final newline : remove BOM from text files translations: unify headers * : fix typos *: trim excess whitespace 2021-09-04 21:59:25 +02:00			`<a href="Documentation.html">Documentation</a>`
Add HTML documentation. 2017-05-13 17:34:16 +02:00			`<img src="arrow_right.gif" alt=">>" style="margin-top: 5px">`
			`<a href="Security%20Requirements%20and%20Precautions.html">Security Requirements and Precautions</a>`
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			`<a href="Trim%20Operation.html">Trim Operation</a>`
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			`<div class="wikidoc">`
			`<h1>Trim Operation</h1>`
			`<div style="text-align:left; margin-top:19px; margin-bottom:19px; padding-top:0px; padding-bottom:0px">`
			`Some storage devices (e.g., some solid-state drives, including USB flash drives) use so-called 'trim' operation to mark drive sectors as free e.g. when a file is deleted. Consequently, such sectors may contain unencrypted zeroes or other undefined data (unencrypted)`
Documentation: Add more information about TRIM behavior in VeraCrypt 2023-11-05 18:06:20 +01:00			`even if they are located within a part of the drive that is encrypted by VeraCrypt.<br>`
			`<br>`
			`On Windows, VeraCrypt allows users to control the trim operation for both non-system and system volumes:`
			`<ul>`
			`<li>For non-system volumes, trim is blocked by default. Users can enable trim through VeraCrypt's interface by navigating to "Settings -> Performance/Driver Configuration" and checking the option "Allow TRIM command for non-system SSD partition/drive."</li>`
			`<li>For <a href="System%20Encryption.html">system encryption</a>, trim is enabled by default (unless a <a href="Hidden%20Operating%20System.html">hidden operating system</a> is running). Users can disable trim by navigating to "System -> Settings" and checking the option "Block TRIM command on system partition/drive."</li>`
			`</ul>`

			`Under Linux, VeraCrypt does not block the trim operation on volumes using the native Linux kernel cryptographic services, which is the default setting. To block TRIM on Linux, users should either enable the "do not use kernel cryptographic services" option in VeraCrypt's Preferences (applicable only to volumes mounted afterward) or use the <code>--mount-options=nokernelcrypto</code> switch in the command line when mounting.`
			`<br>`
			`<br>`
Documentation: Mention that TRIM is not supported on macOS 2023-11-05 18:25:23 +01:00			`Under macOS, VeraCrypt does not support the trim operation. Therefore, trim is always blocked on all volumes.`
			`<br>`
			`<br>`
Documentation: Add more information about TRIM behavior in VeraCrypt 2023-11-05 18:06:20 +01:00			`In cases where trim operations occur, the adversary will be able to tell which sectors contain free space (and may be able to use this information for`
Add HTML documentation. 2017-05-13 17:34:16 +02:00			`further analysis and attacks) and <a href="Plausible%20Deniability.html" style="text-align:left; color:#0080c0; text-decoration:none.html">`
Documentation: Add more information about TRIM behavior in VeraCrypt 2023-11-05 18:06:20 +01:00			`plausible deniability</a> may be negatively affected. In order to avoid these issues, users should either disable trim in VeraCrypt settings as previously described or make sure VeraCrypt volumes are not located on drives that use the trim operation.</div>`
Add HTML documentation. 2017-05-13 17:34:16 +02:00			`<p>To find out whether a device uses the trim operation, please refer to documentation supplied with the device or contact the vendor/manufacturer.</p>`
Minor cleanup of the repo (#822) * : source files should not be executable : make sure files have final newline : remove BOM from text files translations: unify headers * : fix typos *: trim excess whitespace 2021-09-04 21:59:25 +02:00			`</div><div class="ClearBoth"></div></body></html>`