Added info about the use of asymetirc keys to allow for a different keyset on each API domain used.

Signed-off-by: Exadra37 <exadra37@gmail.com>

Author: Exadra37

README.md

@@ -23,6 +23,12 @@ Now, register the API domain for which Approov will issues tokens:
 approov api -add api.example.com
 ```
 
+> **NOTE:** By default a symmetric key (HS256) is used to sign the Approov token on a valid attestation of the mobile app for each API domain it's added with the Approov CLI, so that all APIs will share the same secret and the backend needs to take care to keep this secret secure.
+>
+> A more secure alternative is to use asymmetric keys (RS256 or others) that allows for a different keyset to be used on each API domain and for the Approov token to be verified with a public key that can only verify, but not sign, Approov tokens.
+>
+> To implement the asymmetric key you need to change from using the symmetric HS256 algorithm to an asymmetric algorithm, for example RS256, that requires you to first [add a new key](https://approov.io/docs/latest/approov-usage-documentation/#adding-a-new-key), and then specify it when [adding each API domain](https://approov.io/docs/latest/approov-usage-documentation/#keyset-key-api-addition). Please visit [Managing Key Sets](https://approov.io/docs/latest/approov-usage-documentation/#managing-key-sets) on the Approov documentation for more details.
+
 Next, enable your Approov `admin` role with:
 
 ```bash

docs/APPROOV_TOKEN_BINDING_QUICKSTART.md

@@ -49,11 +49,17 @@ Approov needs to know the domain name of the API for which it will issue tokens.
 
 Add it with:
 
-```text
+```bash
 approov api -add your.api.domain.com
 ```
 
-Adding the API domain also configures the [dynamic certificate pinning](https://approov.io/docs/latest/approov-usage-documentation/#approov-dynamic-pinning) setup, out of the box.
+> **NOTE:** By default a symmetric key (HS256) is used to sign the Approov token on a valid attestation of the mobile app for each API domain it's added with the Approov CLI, so that all APIs will share the same secret and the backend needs to take care to keep this secret secure.
+>
+> A more secure alternative is to use asymmetric keys (RS256 or others) that allows for a different keyset to be used on each API domain and for the Approov token to be verified with a public key that can only verify, but not sign, Approov tokens.
+>
+> To implement the asymmetric key you need to change from using the symmetric HS256 algorithm to an asymmetric algorithm, for example RS256, that requires you to first [add a new key](https://approov.io/docs/latest/approov-usage-documentation/#adding-a-new-key), and then specify it when [adding each API domain](https://approov.io/docs/latest/approov-usage-documentation/#keyset-key-api-addition). Please visit [Managing Key Sets](https://approov.io/docs/latest/approov-usage-documentation/#managing-key-sets) on the Approov documentation for more details.
+
+Adding the API domain also configures the [dynamic certificate pinning](https://approov.io/docs/latest/approov-usage-documentation/#dynamic-pinning) setup, out of the box.
 
 > **NOTE:** By default the pin is extracted from the public key of the leaf certificate served by the domain, as visible to the box issuing the Approov CLI command and the Approov servers.
 

docs/APPROOV_TOKEN_QUICKSTART.md

@@ -49,11 +49,17 @@ Approov needs to know the domain name of the API for which it will issue tokens.
 
 Add it with:
 
-```text
+```bash
 approov api -add your.api.domain.com
 ```
 
-Adding the API domain also configures the [dynamic certificate pinning](https://approov.io/docs/latest/approov-usage-documentation/#approov-dynamic-pinning) setup, out of the box.
+> **NOTE:** By default a symmetric key (HS256) is used to sign the Approov token on a valid attestation of the mobile app for each API domain it's added with the Approov CLI, so that all APIs will share the same secret and the backend needs to take care to keep this secret secure.
+>
+> A more secure alternative is to use asymmetric keys (RS256 or others) that allows for a different keyset to be used on each API domain and for the Approov token to be verified with a public key that can only verify, but not sign, Approov tokens.
+>
+> To implement the asymmetric key you need to change from using the symmetric HS256 algorithm to an asymmetric algorithm, for example RS256, that requires you to first [add a new key](https://approov.io/docs/latest/approov-usage-documentation/#adding-a-new-key), and then specify it when [adding each API domain](https://approov.io/docs/latest/approov-usage-documentation/#keyset-key-api-addition). Please visit [Managing Key Sets](https://approov.io/docs/latest/approov-usage-documentation/#managing-key-sets) on the Approov documentation for more details.
+
+Adding the API domain also configures the [dynamic certificate pinning](https://approov.io/docs/latest/approov-usage-documentation/#dynamic-pinning) setup, out of the box.
 
 > **NOTE:** By default the pin is extracted from the public key of the leaf certificate served by the domain, as visible to the box issuing the Approov CLI command and the Approov servers.