This article discusses how to generate an encrypted private key and public certificate pair that is suitable for use with HTTPS, FTPS, and the administrative port for Secure FTP Server-FIPS. (To generate an unencrypted key/certificate pair, refer to Generating an Unencrypted Private Key and Self-Signed Public Certificate.)
General Information
When operating in a FIPS-approved mode, PKI key/certificates must be between 1024- bits and 4096-bits, inclusive.
The supported cipher combinations allowed for SSL negotiation are limited to:
SSLv3/TLSv1 - RSA Key Exchange, RSA Authentication, 256 bit AES encryption, and SHA1 HMAC
SSLv3/TLSv1 - RSA Key Exchange, RSA Authentication, 168 bit 3DES encryption, and SHA1 HMAC
SSLv3/TLSv1 - RSA Key Exchange, RSA Authentication, 128 bit AES encryption, and SHA1 HMAC
Each of the above combinations uses RSA key exchange; therefore, RSA based key/certificates must be used.
In FIPS mode, the private key must use the PKCS#8 format and PKCS#12 compatible encryption of the private key, which allows the use of the necessary strong encryption algorithm of 3DES encryption and SHA1 hashing.
Procedure
These instructions assume you have downloaded and installed the Windows binary distribution of OpenSSL. Refer to Using OpenSSL for the general instructions
Generate an unencrypted RSA private key:
>C:\Openssl\bin\openssl.exe genrsa -out <Key Filename> <Key Size>
Where:
<Key Filename> is the desired filename for the private key file
<Key Size> is the desired key length of either 1024, 2048, or 4096
For example, type:
>C:\Openssl\bin\openssl.exe genrsa -out my_key.key 2048
Encrypted the unencrypted private key:
>C:\Openssl\bin\openssl.exe pkcs8 -v1 PBE-SHA1-3DES -topk8 -in <Unencrypted Key Filename> -out <Encrypted Key Filename>
Where:
<Unencrypted Key Filename> is the input filename of the previously generated unencrypted private key.
<Encrypted Key Filename> is the output filename of the encrypted private key
For example, type:
>C:\Openssl\bin\openssl.exe pkcs8 -v1 PBE-SHA1-3DES -topk8 -in my_key.key -out my_encrypted_key.key
Delete the unencrypted private key.
Generate a Certificate Signing Request:
In version 0.9.8g:
>C:\Openssl\bin\openssl.exe req -new -key <Encrypted Key Filename> -out <Request Filename> -config C:\Openssl\bin\openssl.cnf
-OR-
In version 0.9.8h and later:
>C:\Openssl\bin\openssl.exe req -new -key <Encrypted Key Filename> -out <Request Filename> -config C:\Openssl\bin\openssl.cfg
Where:
<Encrypted Key Filename> is the input filename of the encrypted private key
<Request Filename> is the output filename of the certificate signing request
For example, type:
>C:\Openssl\bin\openssl.exe req -new -key my_encrypted_key.key -out my_request.csr -config C:\Openssl\bin\openssl.cnf
Follow the on-screen prompts for the required certificate request information.
Generate a self-signed public certificate based on the request:
>C:\Openssl\bin\openssl.exe x509 -req -days 3650 -in <Request Filename> -signkey <Encrypted Key Filename> -out <Certificate Filename>
Where:
<Request Filename> is the input filename of the certificate signing request
<Encrypted Key Filename> is the input filename of the encrypted private key
<Certificate Filename> is the output filename of the public certificate
For example, type:
>C:\Openssl\bin\openssl.exe x509 -req -days 3650 -in my_request.csr -signkey my_encrypted_key.key -out my_cert.crt
(Optional) You may now delete the request file as it is no longer needed.
The resulting encrypted private key file and public certificate file can now be used with Secure FTP Server - FIPS.