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What is JVM startup parameter: -XX:[+|-]UseAES?

What is JVM startup parameter: -XX:[+|-]UseAES? Have you used this JVM arguement before? What are the pros & cons of using this Java argument? Can you share your perspective/experience in using this JVM argument?

  • jvmargument

  • xx-useaes

  • x-useaes

  • JVM startup parameter

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Pavel Khodakovsky

Usage:                                                    

 

The option “-XX:[+|-]UseAES” controls whether AES instructions are used when available.

 

Since:

 

Starting from JDK 7.

 

Syntax:

 

java -XX:[+|-]UseAES MainClass

 

Examples:

  • To enable hardware-based AES intrinsics: java -XX:+UseAES MainClass
  • To disable hardware-based AES intrinsics: java -XX:-UseAES MainClass

Description:

 

Before introducing the flag “UseAES”, we should explain what is AES?

 

AES is a specification for the encryption of electronic data established based on a design principle known as a substitution–permutation network, and is efficient in both software and hardware. Unlike its predecessor DES, AES does not use a Feistel network. AES is a variant of Rijndael, with a fixed block size of 128 bits, and a key size of 128, 192, or 256 bits. By contrast, Rijndael per se is specified with block and key sizes that may be any multiple of 32 bits, with a minimum of 128 and a maximum of 256 bits.

 

AES operates on a 4 × 4 column-major order array of bytes, termed the state. Most AES calculations are done in a particular finite field.

 

While most modern hardware systems (2010 and newer) enable AES Intrinsics by default for better performance. A good example would be databases which uses SSL/TLS encryption, they take advantages of hardware acceleration intrinsic on its machine. Java introduced the parameter “UseAES” to also take advantage of AES hardware acceleration, this flag allows you to enable/disable he use of hardware-based AES for Intel, AMD, and SPARC hardware. The “-XX:+UseAES” is used in conjunction with “UseAESIntrinsics”.

 

The supported hardwares are Intel Westmere (2010 and newer), AMD Bulldozer (2011 and newer), or SPARC (T4 and newer).

 

Flags that control intrinsics now require the option “-XX:+UnlockDiagnosticVMOptions”.

 

This option enables hardware-based AES for Intel, AMD, and SPARC hardware. Intel Westmere (2010 and newer), AMD Bulldozer (2011 and newer), and SPARC (T4 and newer) are the supported hardware.

 

Default Value:

 

This option is disabled by default.

 

Errors:

 

None.

 

Arguments related:

 

UseAESIntrinsics.

 

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