What is Hashing?
Understanding the digital fingerprints that power blockchain proof
The Basics
A hash is like a digital fingerprint for any piece of data — a file, a message, or anything else. When you run data through a hash function, it produces a fixed-length string of characters that uniquely represents that data.
Three key properties make hashing useful:
- Deterministic — the same input always produces the exact same hash, every time, on any computer
- One-way — you cannot reverse a hash to recover the original data
- Sensitive to change — even a single character difference produces a completely different hash
What is SHA256?
SHA256 is a specific hash algorithm that produces a 256-bit output, displayed as 64 hexadecimal characters. It is an industry standard used widely in security, software verification, and blockchain technology.
Example: the SHA256 hash of "Hello"
185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969
Change "Hello" to "hello" (just the capitalization) and the hash is entirely different. This sensitivity is what makes hashing a reliable way to verify that data has not been altered.
Why Does This Matter?
When you record a hash on the blockchain, you are creating permanent proof that a specific piece of data existed in that exact form at that point in time. Later, anyone can take the original file, compute its hash, and compare it to the on-chain record.
If the hashes match, it proves the file is unchanged since the moment it was recorded. This is the foundation behind proof of existence — a powerful concept for contracts, creative works, research, legal documents, and more.
How AlwaysProof Uses Hashing
Both of our products use SHA256 hashing to create blockchain-backed proof:
- Information Sheet NFTs — include SHA256 or SHA512 hashes as items in your NFT, alongside messages and other data
- Blockchain Proof — write a SHA256 hash directly to the blockchain using a credit card
Try It Yourself
You can compute SHA256 hashes on your own computer using built-in tools:
Linux:
sha256sum yourfile.pdfmacOS:
shasum -a 256 yourfile.pdfWindows (PowerShell):
Get-FileHash yourfile.pdf -Algorithm SHA256The hash you get should match exactly what AlwaysProof computes for the same file. That is the power of deterministic hashing — anyone, anywhere can independently verify.