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The client_id is normally supplied by Buypass. See also Client authentication.
Client credentials
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The client authentication method will depend on the Security Domain and the rules and policies associated with the domain.
For example, for the BuypassID Domain, only the private_key_jwt is currently supported. Hence a certificate or public key is needed. Type Use of certificate (self-signed or Qualified) will depend on the Security domain and Use-Case). Note that the the the certificate/public key can jwks_uri (se RFC 7517) may be supported at a later date for this domain.
For other domains, public keys may also be provided using a jwks_uri (se RFC 7517), enabling the client to control key-rotation independently of certificate expirations.For test purposes
Finally, some domains (low risk) may allow client_secret_basic or client_secret_post may be considered.with some level of self service for generating secrets
See also Client authentication.
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