Některé hostingové společnosti, nebo jiné aplikace vyžadují kromě certifikátu s příponou *.crt ještě mít primární klíč.

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Customers sometimes have a need to export a certificate and private key from a Windows computer to separate certificate and key files for use elsewhere. Windows doesn't provide the means to complete this process.

Exporting Certificates from the Windows Certificate Store describes how to export a certificate and private key into a single .pfx file. Follow the procedure below to extract separate certificate and private key files from the .pfx file.

Extracting Certificate and Private Key Files from a .pfx File

1.Take the file you exported (e.g. certname.pfx) and copy it to a system where you have OpenSSL installed.
Note: the *.pfx file is in PKCS#12 format and includes both the certificate and the private key.

2. command to export the private key: openssl pkcs12 -in certname.pfx -nocerts -out key.pem -nodes
3. command to export the certificate: openssl pkcs12 -in certname.pfx -nokeys -out cert.pem
4. command to remove the passphrase from the private key: openssl rsa -in key.pem -out server.key

Aplikace OpenSSL