Create code signing certificate

Management summary

  1. You generate certificate signing request on your machine (using certmgr or ActiveX component).
  2. Private/public key pair is generated along with the request (on your machine).
  3. You export certificate that represents the request from your certificate key store.
  4. You extract private key from the certificate that represents the request.
  5. You send the request (it contains public key only) to CA (or ActiveX does this automatically).
  6. CA sends your certificate back (crt file that is basically your public key, signed with CA’s keys).
  7. Finally you need to combine the private key and the crt to create a pfx, that contains both private key and the certificate.

Important points

  • Private key is generated along with the certificate request.
  • Private key is generated on your machine.
  • Private key is never sent to CA (Certificate Authority).
  • Certificate received from the CA (*.crt file) doesn’t contain your private key.
    • Generate CSR & private key – ActiveX

      Some vendors, like Comodo, use Active X component, that runs on your machine and creates certificate request along with private/public key pair generation on your machine:

      activex_01

      Private key can be found in the certmgr of the local account (not machine’s):

      activex_02

      Later on it must be exported as a pfx (e.g. “Request.pfx”).

      Generate CSR & private key – CertMgr

      In MMC (certmgr), expand Certificates (Local Computer) and then Personal.
      Right-click Certificates, and then go to the following menus: All Tasks > Advanced Operations > Create Custom Request:

      certmgr_00

      Click Next:

      certmgr_01

      Click Next:

      certmgr_02

      Click Next:

      certmgr_03

      Ensure the Request format is PKCS #10, and then click Next:

      certmgr_04

      Click the downward-facing arrow next to Details, and then click Properties.

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      On the subject type, select the following values, enter the corresponding Value, and then click Add:

      • Common name – Your business or organization’s name
      • Organization – Your business or organization’s name
      • Locality – Your business or organization’s address
      • State – The state where your business or organization resides
      • Country – The country where your business or organization resides

      Go to the Private Key tab, click Key type, and then select Make private key exportable:
      Click OK, and then click Next:

      certmgr_07

      Browse for the location where you want to save the file, enter a File Name (“Request.csr”), and then click Finish.
      Your CSR is now stored in the file you saved it to on your local machine.

      certmgr_05

      Request file is regular text file:

      certmgr_15

      This process also creates a private key, which you will need to use later to create a PFX file to sign your code or driver.

      Export certificate that represents the request

      If you were using ActiveX to generate certificate request, certificate that represents the request (including private key) is stored in certmgr of the local account (not machine’s):

      activex_02

      Go to “Certificate Enrollment Requests”/ “Certificates” (Hit refresh if it is empty):

      certmgr_08

      Right-click the certificate and then go to the following menus: All Tasks > Export:

      certmgr_09

      Select export private key and hit Next:

      certmgr_10

      Ensure the Request format is PKCS #12, and then click Next:

      certmgr_11

      Specify password:

      certmgr_12

      Browse for the location where you want to save the file, enter a File Name (“Request.pfx”), and then click Finish.

      certmgr_13

      Click Finish:

      certmgr_14

      Certificate that represents your request is now stored in the file you saved on your local machine. It contains both private and public key.

      Extract private key

      First you’ll need to install OpenSSL.

      To extract private key from the request, issue following command:

      openssl pkcs12 -in Request.pfx -out Request_PrivateKey.pem -nocerts -nodes

      nocerts = private key only,
      nodes = no password

      Generate CSR & private key – OpenSSL

      You can use following command to create certificate request and key using OpenSSL:

      openssl req -new -newkey rsa:2048 -nodes -keyout Request_PrivateKey.key -out Request.csr

      You may need to convert to convert the key (BEGIN PRIVATE KEY) to PKCS#1 format (BEGIN RSA PRIVATE KEY):

      openssl rsa -outform pem -in Request_PrivateKey.key -out Request_PrivateKey.pem

      CA creates a certificate

      Now you should upload -or- copy&paste request file (“Request.csr”) to your CA, and in return, they should create the certificate for you:

      generated_00

      What you receive from your CA looks more or less like this:
      generated_01

      Most important file is the crt file which contains your certificate (it includes public key only).

      Combine private key with cert to create pfx

      To combine private key from the request and certificate from CA into one pfx certificate, issue following command:

      openssl pkcs12 -inkey Request_PrivateKey.pem -in 00…70.crt -export -out 00…70.pfx

      The pfx file you created contains both private key and the certificate and can be used to sign your code.

Questions?

Consider using our Q&A forum for asking any questions.