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Every file AuthenSeal issues includes a SHA-256 cryptographic hash. This 64-character string is mathematically derived from every single byte of your file. It is the bedrock of content integrity verification.
How hashing works
A hash function takes an input of any size and produces a fixed-length output. For SHA-256, that output is always 256 bits (64 hex characters). The function has two critical properties:
SHA-256("Hello") = 185f8db32921bd46d35b9e…
Even changing a single pixel in an image will produce a completely different hash — this is called the "avalanche effect" and it's what makes hashing so powerful for integrity verification.
What a hash proves — and what it doesn't
A SHA-256 hash proves three things:
- The exact bytes of the file at the moment it was hashed
- Any subsequent modification — even one bit — will produce a different hash
- Two files with the same hash are (for all practical purposes) identical
SHA-256 vs SHA-512 — does it matter?
AuthenSeal stores both SHA-256 and SHA-512 hashes. SHA-256 is the industry standard for content integrity and is used in Bitcoin, TLS, and most code signing workflows. SHA-512 provides additional security margin and is preferred in some high-security contexts. For content certification purposes, SHA-256 is more than sufficient — but having both gives you maximum interoperability.