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<title>VeraCrypt - Free Open source disk encryption with strong security for the Paranoid</title>
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<a href="Hardware%20Acceleration.html">Hardware Acceleration</a>
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<h1>Hardware Acceleration</h1>
<div style="text-align:left; margin-top:19px; margin-bottom:19px; padding-top:0px; padding-bottom:0px">
Some processors (CPUs) support hardware-accelerated <a href="AES.html" style="text-align:left; color:#0080c0; text-decoration:none.html">
AES</a> encryption,* which is typically 4-8 times faster than encryption performed by the purely software implementation on the same processors.</div>
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By default, VeraCrypt uses hardware-accelerated AES on computers that have a processor where the Intel AES-NI instructions are available. Specifically, VeraCrypt uses the AES-NI instructions that perform so-called AES rounds (i.e. the main portions of the AES
algorithm).** VeraCrypt does not use any of the AES-NI instructions that perform key generation.</div>
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Note: By default, VeraCrypt uses hardware-accelerated AES also when an encrypted Windows system is booting or resuming from hibernation (provided that the processor supports the Intel AES-NI instructions).</div>
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To find out whether VeraCrypt can use hardware-accelerated AES on your computer, select
<em style="text-align:left">Settings</em> > <em style="text-align:left">Performance/</em><em>Driver Configuration</em> and check the field labeled '<em style="text-align:left">Processor (CPU) in this computer supports hardware acceleration for AES</em>'.</div>
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To find out whether a processor you want to purchase supports the Intel AES-NI instructions (also called "AES New Instructions"), which VeraCrypt uses for hardware-accelerated AES, please check the documentation for the processor or contact the vendor/manufacturer.
Alternatively, click <a href="http://ark.intel.com/search/advanced/?AESTech=true" style="text-align:left; color:#0080c0; text-decoration:none">
here</a> to view an official list of Intel processors that support the AES-NI instructions. However, note that some Intel processors, which the Intel website lists as AES-NI-supporting, actually support the AES-NI instructions only with a Processor Configuration
update (for example, i7-2630/2635QM, i7-2670/2675QM, i5-2430/2435M, i5-2410/2415M). In such cases, you should contact the manufacturer of the motherboard/computer for a BIOS update that includes the latest Processor Configuration update for the processor.</div>
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If you want to disable hardware acceleration of AES (e.g. because you want VeraCrypt to use only a fully open-source implementation of AES), you can do so by selecting<em style="text-align:left"> Settings</em> >
<em style="text-align:left">Performance and Driver Options </em>and disabling the option '<em style="text-align:left">Accelerate AES encryption/decryption by using the AES instructions of the processor</em>'. Note that when this setting is changed, the operating
system needs to be restarted to ensure that all VeraCrypt components internally perform the requested change of mode. Also note that when you create a VeraCrypt Rescue Disk, the state of this option is written to the Rescue Disk and used whenever you boot
from it (affecting the pre-boot and initial boot phase). To create a new VeraCrypt Rescue Disk, select
<em style="text-align:left">System</em> > <em style="text-align:left">Create Rescue Disk</em>.</div>
<p> </p>
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<p><span style="text-align:left; font-size:10px; line-height:12px">* In this chapter, the word 'encryption' also refers to decryption.</span><br style="text-align:left">
<span style="text-align:left; font-size:10px; line-height:12px">** Those instructions are
<em style="text-align:left">AESENC</em>, <em style="text-align:left">AESENCLAST</em>,
<em style="text-align:left">AESDEC</em>, and <em style="text-align:left">AESDECLAST</em> and they perform the following AES transformations:
<em style="text-align:left">ShiftRows</em>, <em style="text-align:left">SubBytes</em>,
<em style="text-align:left">MixColumns</em>, <em style="text-align:left">InvShiftRows</em>,
<em style="text-align:left">InvSubBytes</em>, <em style="text-align:left">InvMixColumns</em>, and
<em style="text-align:left">AddRoundKey</em> (for more details about these transformations, see [3])</span><span style="text-align:left; font-size:10px; line-height:12px">.</span></p>
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