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---
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layout: docs
page_title: Entropy Augmentation - Configuration
description: >-
Entropy augmentation enables Vault to sample entropy from external
cryptographic modules.
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---
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# `Entropy augmentation` seal
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Entropy augmentation enables Vault to sample entropy from external cryptographic modules.
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Sourcing external entropy is done by configuring a supported [Seal](/vault/docs/configuration/seal) type which
include: [PKCS11 seal](/vault/docs/configuration/seal/pkcs11), [AWS KMS](/vault/docs/configuration/seal/awskms), and
[Vault Transit](/vault/docs/configuration/seal/transit).
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Vault Enterprises's external entropy support is activated by the presence of an `entropy "seal"`
block in Vault's configuration file.
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## Requirements
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A valid Vault Enterprise license is required for Entropy Augmentation.
~> **Warning** This feature is not available with FIPS 140-2 Inside variants of Vault.
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Additionally, the following software packages and enterprise modules are required for sourcing entropy
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via the [PKCS11 seal](/vault/docs/configuration/seal/pkcs11):
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- Vault Enterprise with the Plus package
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- PKCS#11 compatible HSM integration library. Vault targets version 2.2 or
higher of PKCS#11. Depending on any given HSM, some functions (such as key
generation) may have to be performed manually.
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- The [GNU libltdl library](https://www.gnu.org/software/libtool/manual/html_node/Using-libltdl)
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— ensure that it is installed for the correct architecture of your servers
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## `entropy` example
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This example shows configuring entropy augmentation through a PKCS11 HSM seal from Vault's configuration
file:
```hcl
seal "pkcs11" {
...
}
entropy "seal" {
mode = "augmentation"
}
```
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For a more detailed tutorial, visit the [HSM Entropy Challenge](/vault/tutorials/enterprise/hsm-entropy)
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on HashiCorp's Learn website.
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## `entropy augmentation` parameters
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These parameters apply to the `entropy` stanza in the Vault configuration file:
- `mode` `(string: <required>)`: The mode determines which Vault operations requiring
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entropy will sample entropy from the external source. Currently, the only mode supported
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is `augmentation` which sources entropy for [Critical Security Parameters (CSPs)](/vault/docs/enterprise/entropy-augmentation#critical-security-parameters-csps).
