OWASP Cheat Sheet Series: Key Management Cheat Sheet

# Key Management Cheat Sheet

## Introduction

This Key Management Cheat Sheet provides developers with guidance for implementation of cryptographic key management within an application in a secure manner. It is important to document and harmonize rules and practices for:

1. Key life cycle management (generation, distribution, destruction)
2. Key compromise, recovery and zeroization
3. Key storage
4. Key agreement

## General Guidelines and Considerations

Formulate a plan for the overall organization's cryptographic strategy to guide developers working on different applications and ensure that each application's cryptographic capability meets minimum requirements and best practices.

Identify the cryptographic and key management requirements for your application and map all components that process or store cryptographic key material.

## Key Selection

Selection of the cryptographic and key management algorithms to use within a given application should begin with an understanding of the objectives of the application.

For example, if the application is required to store data securely, then the developer should select an algorithm suite that supports the objective of data at rest protection security. Applications that are required to transmit and receive data would select an algorithm suite that supports the objective of data in transit protection.

We have provided recommendations on the selection of crypto suites within an application based on application and security objectives. Application developers oftentimes begin the development of crypto and key management capabilities by examining what is available in a library.

However, an analysis of the real needs of the application should be conducted to determine the optimal key management approach. Begin by understanding the security objectives of the application which will then drive the selection of cryptographic protocols that are best suited. For example, the application may require:

1. Confidentiality of data at rest and confidentiality of data in transit.
2. Authenticity of the end device.
3. Authenticity of data origin.
4. Integrity of data in transit.
5. Keys to create the data encryption keys.

Once the understanding of the security needs of the application is achieved, developers can determine what protocols and algorithms are required. Once the protocols and algorithms are understood, you can begin to define the different types of keys that will support the application's objectives.

There are a diverse set of key types and certificates to consider, for example:

1. **Encryption:** [Symmetric](https://en.wikipedia.org/wiki/Symmetric-key_algorithm) encryption keys, [Asymmetric](https://en.wikipedia.org/wiki/Public-key_cryptography) encryption keys (public and private).
2. **Authentication of End Devices:** Pre-shared symmetric keys, Trusted certificates, Trust Anchors.
3. **Data Origin Authentication:** [HMAC](https://en.wikipedia.org/wiki/HMAC).
4. **Integrity Protection:** [Message Authentication Codes](https://en.wikipedia.org/wiki/Message_authentication_code) (MACs).
5. **Key Encryption Keys**.

### Algorithms and Protocols

According to `NIST SP 800-57 Part 1`, many algorithms and schemes that provide a security service use a [hash function](https://en.wikipedia.org/wiki/Hash_function) as a component of the algorithm.

Hash functions can be found in digital signature algorithms (`FIPS186`), Keyed-Hash Message Authentication Codes (HMAC) (`FIPS198`), key-derivation functions/methods (`NIST Special Publications (SP) 800-56A, 800-56B, 800-56C and 800-108`), and random number generators (`NIST SP 800-90A`). Approved hash functions are defined in `FIPS180`.

`NIST SP 800-57 Part 1` recognizes three basic classes of approved cryptographic algorithms: hash functions, symmetric- key algorithms and asymmetric-key algorithms. The classes are defined by the number of cryptographic keys that are used in conjunction with the algorithm.

The NSA released a report, [Commercial National Security Algorithm Suite 2.0](https://media.defense.gov/2025/May/30/[PII_REDACTED]/-1/-1/0/CSA_CNSA_2.0_ALGORITHMS.PDF) which lists the cryptographic algorithms that are expected to be remain strong even with advances in quantum computing.

#### Cryptographic hash functions

Cryptographic hash functions do not require keys. Hash functions generate a relatively small digest (hash value) from a (possibly) large input in a way that is fundamentally difficult to reverse (i.e., it is hard to find an input that will produce a given output). Hash functions are used as building blocks for key management, for example,

1. To provide data authentication and integrity services (Section 4.2.3) – the hash function is used with a key to generate a message authentication code.
2. To compress messages for digital signature generation and verification (Section 4.2.4).
3. To derive keys in key-establishment algorithms (Section 4.2.5).
4. To generate deterministic random numbers (Section 4.2.7).

#### Symmetric-key algorithms

Symmetric-key algorithms (sometimes known as secret-key algorithms) transform data in a way that is fundamentally difficult to undo without knowledge of a secret key. The key is "symmetric" because the same key is used for a cryptographic operation and its inverse (e.g., encryption and decryption).

Symmetric keys are often known by more than one entity; however, the key shall not be disclosed to entities that are not authorized access to the data protected by that algorithm and key. Symmetric key algorithms are used, for example,

1. To provide data confidentiality (Section 4.2.2); the same key is used to encrypt and decrypt data.
2. To provide authentication and integrity services (Section 4.2.3) in the form of Message Authentication Codes (MACs); the same key is used to generate the MAC and to validate it. MACs normally employ either a symmetric key-encryption algorithm or a cryptographic hash function as their cryptographic primitive.
3. As part of the key-establishment process (Section 4.2.5).
4. To generate deterministic random numbers (Section 4.2.7).

#### Asymmetric-key algorithms

Asymmetric-key algorithms, commonly known as public-key algorithms, use two related keys (i.e., a key pair) to perform their functions: a public key and a private key. The public key may be known by anyone; the private key should be under the sole control of the entity that "owns" the key pair. Even though the public and private keys of a key pair are related, knowledge of the public key does not reveal the private key. Asymmetric algorithms are used, for example,

1. To compute digital signatures (Section 4.2.4).
2. To establish cryptographic keying material (Section 4.2.5).
3. To generate random numbers (Section 4.2.7).

#### Message Authentication Codes (MACs)

Message Authentication Codes (MACs) provide data authentication and integrity. A MAC is a cryptographic checksum on the data that is used in order to provide assurance that the data has n