Every POS transaction posted in the Norwegian version of LS Central is automatically signed with a digital signature, as required by the Norwegian cash register regulation. The signature is generated when the transaction is posted and stored on the new Transaction Signature table, separately from the transaction header.
How the signature is generated
Each signature is produced as follows:
- The system builds an input string from the transaction. The string concatenates, in order, the previous transaction's signature on the same store and terminal, the transaction date, time, transaction number, gross amount (including income/expense entries), and net amount (including income/expense entries). Fields are separated by
;and use a culture-invariant numeric format. - The input string is hashed with SHA-1.
- The hash is signed with the private key of the Norwegian_Tax certificate.
- The Base64-encoded signature is stored on the Transaction Signature record, together with the certificate thumbprint as the Private Key Version.
Because every transaction signature includes the previous transaction's signature, the signed transactions form an unbroken chain — any modification to a posted transaction breaks both that transaction's signature and every signature that follows it.
Certificate storage
The signing certificate must be uploaded to the Business Central isolated certificate store of the company that runs the POS. The certificate must be named Norwegian_Tax; the system looks it up by that name on the Isolated Certificate table and filters by the current company. If the certificate is missing, the system raises the error Certificate Norwegian_Tax not found.
See How to: Upload a Certificate for how to upload the certificate.
See also
View the Transaction Signature
How to: Verify a Transaction Signature