What is hashing? How is it used in security encryption?

Excerpt

Hashing is the process of converting any data into a fixed-length string or hash value. This post looks at what hashing is, common algorithms like SHA256 and bcrypt, and varied uses of hashing in encrypting passwords, verifying data integrity, blockchain, etc.

Encryption and hashing are two fundamental concepts in cybersecurity that protect sensitive data and transactions online. In this post, we’ll look at what hashing is, how it complements encryption, and its varied uses in security implementations.

Introduction

Encryption transforms data into an unreadable cipher text to keep it confidential. It requires a secret key or password to reverse the encryption and get the original plaintext back.

Hashing is the process of converting any data into a fixed-length string of text known as a hash value, or simply a hash. It is a one-way function, so you cannot recover the original data from the hash.

Hashing plays a critical role alongside encryption to protect passwords, validate integrity, authenticate users, and more. Understanding its capabilities and limitations helps build more robust security.

What is Hashing?

Hashing is a mathematical algorithm that takes an input and generates a unique output string of fixed length. Some properties of cryptographic hash functions:

• The output hash is entirely different from the input and cannot be used to retrieve the original data.
• Identical inputs always generate the same hash output.
• Even a small change in the input drastically changes the hash.
• Hashes are one-way and cannot be reversed engineered.
• Hash algorithms are carefully designed to avoid collisions where two different inputs create the same hash.

Popular hashing algorithms include MD5, SHA1, SHA256, SHA512, bcrypt, etc. Each use different internal logic and produce varied hash string lengths.

How is Hashing Used in Security Encryption?

Hashing strengthens encryption implementations in areas like:

Password Storage

Passwords cannot be stored in plain text. Hashing converts passwords into unreadable strings suitable for persistent storage. On login, the entered password is hashed and matched against the stored hash instead of comparing plain texts.

Message Authentication

Hashing a message before sending and appending its hash ensures message integrity. The recipient repeats the hash to verify the message contents are intact. Any tampering would change the hash.

Digital Signatures

Signing documents involves encrypting their hash instead of the full content for efficiency. Validating the signature decrypts the hash and matches it to a newly generated hash from the document.

Data Deduplication

Hashing finds duplicate data blocks in systems like file storage by comparing hashes instead of full byte-by-byte comparisons. Matching hashes indicate identical data.

Proof of Work

Hashing functions deliberately slow computers down which is useful for cryptocurrency mining and deterring DDoS attacks. Miners compute hashes repeatedly until they satisfy a difficulty target.

So in summary, hashing transforms data into short fixed-length fingerprints useful for efficiently validating integrity, detecting duplicates, proving work, and creating derivations like passwords and signatures.

Common Hashing Algorithms

MD5

MD5 was designed in 1991 as a fast and secure hash ideal for software integrity checking due to its small 128-bit hash size. Security flaws have rendered it obsolete for most uses today.

SHA1

SHA1 outputs a 160-bit hash. Cryptanalysis has revealed theoretical vulnerabilities in it, so newer SHA2 and SHA3 algorithms are preferred.

SHA256

Part of the SHA2 family, it generates a 256-bit hash widely trusted for applications like SSL certificates and Bitcoin.

SHA512

SHA512 produces a more secure 512-bit hash but is slower than SHA256. It offers higher collision resistance.

bcrypt

A password hashing algorithm that is intentionally slow by design. It is configurable to adjust hashing time, which hinders brute force attacks.

Applications of Hashing in Security

Password Storage

Passwords should be individually salted and hashed using algorithms like bcrypt before persisting them to databases. Comparing hashes instead of plain passwords allows secure authentication.

Data Integrity

Cryptographic checksums using SHA256 ensure data has not been altered intentionally or accidentally in transit or storage. This is critical for software updates, forensics, legal compliance, etc.

Digital Signatures

Algorithms like SHA512 hash the document contents efficiently. The hash is then encrypted using the sender’s private key into a signature verifiable by anyone with the public key.

Blockchain Transactions

Transactions include inputs and outputs hashed using SHA256. Linking transactions sequentially prevents double-spending and forks.

Security Considerations for Hashing

Hashing can seem almost magical in its applications but has certain limitations you should be aware of when implementing crypto solutions:

• No hash function is fully collision proof. There is a small probability of two inputs mapping to the same hash.

• Rainbow table attacks can reverse short hashes by brute force. It is critical to salt passwords individually before hashing them.

• Older algorithms like MD5 and SHA1 are vulnerable to theoretical collisions. Always opt for the latest secure hash algorithms.

• Hash outputs should be long enough (256-bits+) to prevent brute forcing and birthday attacks.

• Timing and power analysis attacks can potentially crack hashes by analyzing algorithm execution. Use constant time and randomized hashing.

• Storing hashes alone is useless after a breach. Adopt password rotation and multifactor authentication.

Conclusion

Hashing is an indispensable cryptographic technique empowering a wide range of critical security applications today like encrypted passwords, trusted transactions, ID systems, and digitally signed documents.

Used properly alongside encryption and salting, hashing helps protect sensitive data and defend against fraud. Carefully chosen algorithms minimize collisions. Upgrading outdated hashes periodically is recommended.

For optimal security, combine hashing with encryption, salting and tools like multi-factor authentication. Understand the strengths as well limits of these algorithms when implementing crypto solutions. Used judiciously, hashing can effectively complement encryption to enhance the confidentiality, integrity and authenticity of sensitive systems and data.