Entropy

Plugin: proc.plugin Module: /proc/sys/kernel/random/entropy_avail

Overview

Entropy, a measure of the randomness or unpredictability of data.

In the context of cryptography, entropy is used to generate random numbers or keys that are essential for secure communication and encryption. Without a good source of entropy, cryptographic protocols can become vulnerable to attacks that exploit the predictability of the generated keys.

In most operating systems, entropy is generated by collecting random events from various sources, such as hardware interrupts, mouse movements, keyboard presses, and disk activity. These events are fed into a pool of entropy, which is then used to generate random numbers when needed.

The /dev/random device in Linux is one such source of entropy, and it provides an interface for programs to access the pool of entropy. When a program requests random numbers, it reads from the /dev/random device, which blocks until enough entropy is available to generate the requested numbers. This ensures that the generated numbers are truly random and not predictable.

However, if the pool of entropy gets depleted, the /dev/random device may block indefinitely, causing programs that rely on random numbers to slow down or even freeze. This is especially problematic for cryptographic protocols that require a continuous stream of random numbers, such as SSL/TLS and SSH.

To avoid this issue, some systems use a hardware random number generator (RNG) to generate high-quality entropy. A hardware RNG generates random numbers by measuring physical phenomena, such as thermal noise or radioactive decay. These sources of randomness are considered to be more reliable and unpredictable than software-based sources.

One such hardware RNG is the Trusted Platform Module (TPM), which is a dedicated hardware chip that is used for cryptographic operations and secure boot. The TPM contains a built-in hardware RNG that generates high-quality entropy, which can be used to seed the pool of entropy in the operating system.

Alternatively, software-based solutions such as Haveged can be used to generate additional entropy by exploiting sources of randomness in the system, such as CPU utilization and network traffic. These solutions can help to mitigate the risk of entropy depletion, but they may not be as reliable as hardware-based solutions.

This collector is only supported on the following platforms:

• linux

This collector only supports collecting metrics from a single instance of this integration.

Default Behavior

Auto-Detection

This integration doesn't support auto-detection.

Limits

The default configuration for this integration does not impose any limits on data collection.

Performance Impact

The default configuration for this integration is not expected to impose a significant performance impact on the system.

Metrics

Metrics grouped by scope.

The scope defines the instance that the metric belongs to. An instance is uniquely identified by a set of labels.

Per Entropy instance

This scope has no labels.

Metrics:

Metric	Dimensions	Unit
system.entropy	entropy	entropy

Alerts

The following alerts are available:

Alert name	On metric	Description
lowest_entropy	system.entropy	minimum number of bits of entropy available for the kernel’s random number generator

Setup

Prerequisites

No action required.

Configuration

File

There is no configuration file.

Options

There are no configuration options.

Examples

There are no configuration examples.