Format a PKI certificate chain

This topic describes how to combine multiple DER-encoded and PEM certificates into a single file.

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If you use more than one certificate, follow this procedure to combine them into a single file.

Convert DER-encoded root and intermediate certificates (with .cer, .crt extension) into PEM format. Use the following openssl command:
```
openssl x509 -inform der -in $input-cert-file-name -out $out-cert-file-name-with-pem-extension
```
Concatenate all the PEM certificates into a single file. Ensure that the root certificate is the last one in the list. Use the following command:
```
cat $intermediate-cert-file-1 ... $intermediate-cert-file-N $root-cert-file-with-pem-extension > trust-chain.pem
```
Upload trust-chain.pem when you create the Smart Card IdP. Ensure that no other Smart Card IdPs exist.

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