[PostFinance] What is «SHA-IN signature»?

To verify the data that is submitted to its system (in case of e-Commerce the hidden fields to the payment page), PostFinance requires the secure data verification method SHA.
For each order, your server generates a unique character string (=digest), hashed with the SHA algorithm of your choice: SHA-1, SHA-256 or SHA-512.

https://e-payment-postfinance.v-psp.com/en/en/guides/integration%20guides/e-commerce/security-pre-payment-check#shainsignature

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