Cryptography Tutorials - Herong's Tutorial Notes
Dr. Herong Yang, Version 4.00

keytool - JDK Tool to Manage Certificates Using 'keystore'

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tool introduced in JDK 1.2 to manage keys and certificates using "keystore". "keytool"

This chapter describes some parts of the JCA (Java Cryptography Architecture) which has been included in JDK since 1.1:

  • What is a certificate and a certificate chain?
  • What is "keystore"?
  • What are the functions offered by "keytool"?
  • Examples of using "keytool".

Certificates and Certificate Chains

Certificate: A digitally signed statement from the issuer saying that the public key of the subject has some specific value.

The above definition is copied from the JDK 1.3.1 documentation. It has a couple of important terms:

  • "signed statement" - The certificate must be signed by the issuer with a digital signature.
  • "issuer" - The person or organization who is issuing this certificate.
  • "public key" - The public key of a key pair selected by the subject.
  • "subject" - The person or organization who owns the public key.

X.509 Certificate - A certificate written in X.509 standard format. X.509 standard was introduction in 1988. It requires a certificate to have the following information:

  • Version - X.509 standard version number.
  • Serial Number - A sequence number given to each certificate.
  • Signature Algorithm Identifier - Name of the algorithm used to sign this certificate by the issuer
  • Issuer Name - Name of the issuer.
  • Validity Period - Period during which this certificate is valid.
  • Subject Name - Name of the owner of the public key.
  • Subject Public Key Information - The public key and its related information.

How can you get a certificate for your own public key?

  • Requesting it from a Certificate Authority (CA), like VeriSign, Thawte or Entrust.
  • Doing it yourself - using tools like JDK "keytool" to generate a self-signed certificate.

Certificate Chain: A series of certificates that one certificate signs the public key of the issuer of the next certificate. Usually the top certificate (the first certificate) is self-signed, where issuer signed its own public key.

What is "keystore"?

"keystore" - A database used by JDK "keytool" command and KeyStore class to store your own private keys, and public key certificates you received from someone else. "keystore" supports the following features:

  • Two types of entries: key entries for private keys and certificate entries for public key certificates.
  • A key entry contains the private key and a certificate chain of the corresponding public key.
  • Every entry has a unique alias name.
  • Key entries are protected by separate passwords.
  • "keystore" may have different implementations from different security package providers. The default implementation from Sun is called JKS.

(Continued on next part...)

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Dr. Herong Yang, updated in 2007
Cryptography Tutorials - Herong's Tutorial Notes - keytool - JDK Tool to Manage Certificates Using 'keystore'