https://stackoverflow.com/questions/13732826/convert-pem-to-crt-and-key

Converting Using OpenSSL

These commands allow you to convert certificates and keys to different formats to make them compatible with specific types of servers or software.

• Convert a DER file (.crt .cer .der) to PEM

  openssl x509 -inform der -in certificate.cer -out certificate.pem
  
  

• Convert a PEM file to DER

  openssl x509 -outform der -in certificate.pem -out certificate.der
  
  

• Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM

  openssl pkcs12 -in keyStore.pfx -out keyStore.pem -nodes
  
  You can add -nocerts to only output the private key or add -nokeys to only output the certificates.
  
  

• Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)

  openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt
  
  

• Convert PEM to CRT (.CRT file)

  openssl x509 -outform der -in certificate.pem -out certificate.crt
  
  

OpenSSL Convert PEM

• Convert PEM to DER

  openssl x509 -outform der -in certificate.pem -out certificate.der
  
  

• Convert PEM to P7B

  openssl crl2pkcs7 -nocrl -certfile certificate.cer -out certificate.p7b -certfile CACert.cer
  
  

• Convert PEM to PFX

  openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt
  
  

OpenSSL Convert DER

• Convert DER to PEM

  openssl x509 -inform der -in certificate.cer -out certificate.pem
  
  

OpenSSL Convert P7B

• Convert P7B to PEM

  openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer
  
  

• Convert P7B to PFX

  openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer
  
  openssl pkcs12 -export -in certificate.cer -inkey privateKey.key -out certificate.pfx -certfile CACert.cer
  
  

OpenSSL Convert PFX

• Convert PFX to PEM

  openssl pkcs12 -in certificate.pfx -out certificate.cer -nodes
  
  

Generate rsa keys by OpenSSL