# Authenticate your requests

Build the SHA-512 hash string needed to authenticate a request that saves a customer's payment details on the Hosted Payment Page

An AI skill is available for this guide, get it on the [Skills Marketplace (GitHub)](https://github.com/payroc/skills).

To load the Hosted Payment Page, you need to include a SHA-512 hash in the HASH parameter. The hash authenticates your request and prevents tampering with sensitive values during transit to our gateway.

Because you've already integrated with Hosted Payment Pages to [run a sale](/guides/payments/hosted-payment-page/load-payment-page), you've already added a terminal secret. However, the hash string for saving a customer's payment details is made up of different values.

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## Build and hash the request string

Create a colon-delimited string from specific request parameter values, append your terminal secret, and then convert the string to a SHA-512 hash.

To create the hash string to save a customer's payment details, complete the following steps:

1. Build your hash with your parameter values in the following order:- `[TERMINALID]:[MERCHANTREF]:[DATETIME]:[ACTION]:[SECRET]`
2. Replace the placeholders with actual values:- `3204004:561234:10-02-2026:09:14:54:058:register:example_secret_123`
3. Use a hashing library in your programming language to convert the string to a SHA-512 hash:- `a674cad40ad2c6bb9421c053e254dbe5fa49335babd0360e15a7875b43c1dedb880df5ca000946a1376237a039bd36c33758c1a3a4c396a324d2534fbddacb44`

You send this value in the HASH parameter of your request to load the Hosted Payment Page.

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## Next steps

- [Load the Hosted Payment Page](/guides/payments/hosted-payment-page/save-details-load-payment-page)