Swap the use of the hash and the signing algorithm: compute a secure hash of the critical information, then sign the hash with a public key algorithm, using the private key. Have the server publish the signed hash and the public key (as a barcode graphic or otherwise) as part of the page.

Presence of the public key allows the client to verify that the hash represents the critical information.

However, note that barcoding the signed hash and the key only improves part of the problem. If a complaint arises, someone will still be stuck keying in the numbers that were included in the hash in the right order and without typos.