Generate a .jks keystore using .key and .crt files

Generate a .jks keystore using .key and .crt files :

Notes :

x509 standard assumes a strict hierarchical system of certificate authorities (CAs) for issuing the certificates.

Structure of a certificate :

The structure of an X.509 v3 digital certificate is as follows:

.
Certificate
Version
Serial Number
Algorithm ID
Issuer
Validity
Not Before
Not After
Subject
Subject Public Key Info
Public Key Algorithm
Subject Public Key
Issuer Unique Identifier (Optional)
Subject Unique Identifier (Optional)
Extensions (Optional)
…
Certificate Signature Algorithm
Certificate Signature

Issuer and subject unique identifiers were introduced in Version 2, Extensions in Version 3. Nevertheless, the Serial number must be unique for each certificate issued by a specific CA

Certificate filename extensions :

Common filename extensions for X.509 certificates are:

.pem – (Privacy Enhanced Mail) Base64 encoded DER certificate, enclosed between “—–BEGIN CERTIFICATE—–” and “—–END CERTIFICATE—–”

.cer, .crt, .der – usually in binary DER form, but Base64-encoded certificates are common too (see .pem above)

.p7b, .p7c – PKCS#7 SignedData structure without data, just certificate(s) or CRL(s)

.p12 – PKCS#12, may contain certificate(s) (public) and private keys (password protected)

.pfx – PFX, predecessor of PKCS#12 (usually contains data in PKCS#12 format, e.g, with PFX files generated in IIS)

PKCS#7 is a standard for signing or encrypting (officially called “enveloping”) data. Since the certificate is needed to verify signed data, it is possible to include them in the SignedData structure. A .P7C file is a degenerated SignedData structure, without any data to sign.
PKCS#12 evolved from the PFX (Personal inFormation eXchange) standard and is used to exchange public and private objects in a single file.

Steps :

Tools like in F5 load balancers generate .crt and .key files ( they basically use openssl ).

Here .crt is the signed certificate from a CA and key contains the private key.

These keys and certificates are in PEM format.

– Open both the files in a notepad and copy the contents in it to a new notepad file and save it with extension .pem

– Now we need to convert this .pem to .des

Note : DES is a binary format and non readable whereas PEM are in human readable form.
Note : Make sure OpenSSL is installed ( You can download it from : http://www.slproweb.com/products/Win32OpenSSL.html )

– You can use the following command to convert PEM to DER format.

Command : openssl pkcs8 -topk8 -nocrypt -in key.pem -inform PEM -out key.der -outform DER ( this command will convert the key file (PEM format) containing private key to DER format )

Command : openssl x509 -in cert.pem -inform PEM -out cert.der -outform DER ( This command converts the signed certificate (PEM format) to DER format ).

– Now we need to add the signed certificate and the private key into the keystore.

Keytool does not let you import an existing private key for which you already have a certificate.

– Download and compile the java code from the link below :

Link : http://www.agentbob.info/agentbob/80.html ( ImportKey.java )

Command : javac ImportKey.java

The above code will add the private key and the certificate into a .jks keystore.

Default name of the keystore that will be created : keystore.ImportKey ( you can edit the code and change it to identity.jks )

Default password/passphrase for the private key : importkey ( you can edit the code to make changes in it accordingly )

Default alias name given to this key would be : importkey

Once you have the .class file run the command below to generate the keystore ( i.e identity.jks ) :

Command :  java ImportKey key.der cert.der ( Note the first argument is the key file and the second is the cerificate (both in DER format) )

Note : The keystore is not created in the same directory. You can find it in the root folder ( Eg : C:\Documents and Settings\CoolDragon\… )

– Now import your rootca.crt file into this keystore to complete the chaining of certificates

Command : keytool -import -file rootca.crt -alias -trustcacerts -keystore keystore.ImportKey -storepass importkey

– Now list the certificates of the keystore to check if the chaining is fine :

Command : keytool -v -list -keystore keystore.ImportKey -storepass importkey

Identity.jks file is now ready 🙂