What a SHA-256 Hash Proves and Does Not Prove

A hash value is a fingerprint of a file. This page states plainly what a hash can show and what it cannot.

Not legal advice. This page is general information. Whether a court admits or relies on a chat is for the court; convokeep does not promise admission or any outcome. Ask a qualified lawyer about your case. In Korea, for example, you can also ask the Korea Legal Aid Corporation (☎132).

What does a hash prove?

SHA-256 is a cryptographic hash function that computes a 256-bit value from a file. The same file always gives the same value, and changing even one character changes it. So if the value of the file you hold later matches a value recorded earlier, the file is unchanged since that value was recorded.

What does a hash not prove?

That no messages were deleted or edited before the export.
That the conversation is genuine or complete.
Who sent a message or when.
That a court will accept it.

What about messages I deleted before exporting?

The hash is calculated on the file as of the moment you exported it. Messages that were gone before then cannot be detected from the hash.

Which hashes go into a convokeep PDF?

The integrity page of a Record PDF contains the SHA-256 of the source file and of the transcript data. The PDF's own hash cannot be placed inside the PDF, so it comes in a separate .sha256.txt file. For how to check it, see Chat PDF integrity hash.

How do I check a hash later?

Drag the file onto the hash checker and it calculates the value in your browser and compares it. The file is not uploaded.

Privacy

Reading the file, building the PDF and calculating hashes all happen in your browser. No chat or attachment is uploaded and there is no account. See the privacy policy and the disclaimer.

Related guides

Ready to try it?

Drop your exported .txt file on the convokeep app for a free preview. The first 3 pages are free (watermarked, no integrity page); saving the full PDF is a one-time paid feature. No chat or attachment is uploaded: the file is read in your browser. To check later that a file is unchanged, use the hash checker.

Open the app

This document was generated locally in the user's browser; no content was uploaded.