# Configuring Environment Variables
source: https://developer.mastercard.com/account-to-account-commerce-for-dsp/tutorial/postman-ies-tutorial/step3/index.md

## Configuring Environment Variables {#configuring-environment-variables}

Mastercard has configured a set of pre-defined values that participants must utilise before running the test scripts. These values could be seen under Environments. Participants should only change the field values that are mentioned in the test cases before executing an API.

![Environment Variable](https://static.developer.mastercard.com/content/account-to-account-commerce-for-dsp/uploads/Configure1-ies.png)

## Populating Environment Variables {#populating-environment-variables}

DSPs must configure environment variables in the Postman application so that test scripts produce the expected behaviour when they are run. The table below details the environment variables and the instructions on how to populate each element.

|    Environment Variable     |                       Field Name in API Specifications                       |                          Description                           |                                                                                   Instructions for DSPs                                                                                    |
|-----------------------------|------------------------------------------------------------------------------|----------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| DSP_ID                      | initiatingPartyId \& debtorServiceProviderId \& X-Participant-ID as a header | Unique value assigned by Mastercard to identify a DSP.         | DSP must populate this value before testing any scenario. **NOTE**: Value is defined by Mastercard during your onboarding process. Contact your Mastercard representative for this value.  |
| CSP_REF_ID                  | creditorServiceProviderId                                                    | Unique value assigned by Mastercard to identify a CSP.         | DSPs must populate this value before testing any scenario. **NOTE**: Value is defined by Mastercard during your onboarding process. Contact your Mastercard representative for this value. |
| encryptionCerDSP            | Used in script                                                               | Encryption cert used to encrypt request payload.               | Refer to postman environment and populate public cert in this field.                                                                                                                       |
| responseDecryptionKeyDSP    | Used in script                                                               | This private key is used to response received to DSP from MC.  | Update private key against this environment variable.                                                                                                                                      |
| requestSignKeyDSP           | Used in script                                                               | Private key to sign request.                                   | For signature generation we need private cert key in this environment variable.                                                                                                            |
| responseVerificationCertDSP | Used in script                                                               | Cert to verify response.                                       | To verify response, public cert is assigned to this environment variable.                                                                                                                  |
| requestSignKeyIdDSP         | Used in script                                                               | SKID : identifies the public key contained in the certificate. | Assign SKID from public key.                                                                                                                                                               |
| publicKeyFingerprintDSP     | Used in script                                                               | Hash value calculated from certificate.                        | Assign hash value for certificate.                                                                                                                                                         |
| requestVerificationCertDSP  | Used in script                                                               | Cert to verify signature in request.                           | To verify request signature sent, we need public cert assigned to this env variable.                                                                                                       |