Does AES use SHA-256?

Excerpt

Explore the relationship between AES and SHA-256 in cryptography and understand how they work together to ensure secure communication.

AES and SHA-256 are two of the most widely used cryptographic algorithms today. AES performs encryption to provide data confidentiality. SHA-256 is a hash function used for data integrity and authentication. There is sometimes confusion around whether AES relies on SHA-256 internally. In this post, we’ll clarify the relationship between AES and SHA-256 and see how they complement each other in real-world crypto implementations.

Introduction

AES (Advanced Encryption Standard) and SHA-256 (Secure Hash Algorithm 256-bit) are essential building blocks of modern information security. AES is a symmetric encryption algorithm used to securely exchange confidential data. SHA-256 generates unique data fingerprints that verify integrity and authenticity. While they serve different primary purposes, AES and SHA-256 are often used together to provide end-to-end security. But contrary to popular belief, AES does not actually use SHA-256 internally.

AES (Advanced Encryption Standard)

AES is a standardized, symmetric key block cipher algorithm that has been widely adopted worldwide. Here are its key characteristics:

• Published by NIST in 2001 after being selected through a 5-year competition.

• Uses fixed block size of 128 bits and key sizes of 128, 192 or 256 bits.

• Relies on substitution, permutation, and other transformations on input data.

• Provides strong confidentiality and fast, efficient encryption on hardware and software.

• Used across many applications like encrypted data storage, secure communications, e-commerce, and more.

Overall, AES has become the gold standard for symmetric encryption algorithms thanks to its security, performance and ubiquity.

SHA-256 (Secure Hash Algorithm 256-bit)

SHA-256 is a cryptographic hash algorithm with the following attributes:

• Developed by NSA, published in 2001 as part of the SHA-2 family.

• Produces a 256-bit (32 byte) hash value or message digest.

• Relies on compression and logical operations like modular addition, bitwise operations etc.

• Provides strong collision resistance and one-way hashing.

• Used extensively in blockchain, digital signatures, data integrity verification, and more.

SHA-256 enables fingerprinting data in a secure, irreversible manner essential for many authentication and integrity needs.

Relationship Between AES and SHA-256

Since AES and SHA-256 are both critical cryptography building blocks, it is a common misconception that AES uses SHA-256 in its internal workings. However, this is not accurate:

• AES is an encryption algorithm, SHA-256 is a hashing algorithm - two distinct cryptographic functions.

• AES does not utilize SHA-256 or any hash internally. AES relies solely on symmetric key algorithms like substitution-permutation networks.

• SHA-256 operates independently to generate hashes for integrity and authentication, not for encryption.

So while AES and SHA-256 are often used together, AES does not actually rely on SHA-256 under the hood.

AES and SHA-256 in Practice

Here are some examples of how AES and SHA-256 complement each other in real-world crypto implementations:

• Encrypted storage may use AES for encrypting data, and SHA-256 to hash passwords and keys.

• SSL/TLS relies on AES for secure channels, and SHA-256 for certificate and signature validation.

• Cryptocurrency wallets use AES to encrypt private keys, and SHA-256 in transaction signing.

• Disk encryption solutions combine AES encryption with SHA-256 for integrity verification.

Using both algorithms together provides confidentiality, integrity, and authenticity - principles crucial for robust security.

Conclusion

To summarize, AES and SHA-256 are separate cryptographic algorithms that serve distinct purposes - AES provides encryption, SHA-256 enables secure hashing. While AES does not use SHA-256 in its internals, the two are often implemented together to deliver comprehensive security protections through a defense-in-depth approach. Going forward, both standards will continue evolving to meet modern security and performance needs.