Manages a keystore (database) of cryptographic keys, X.509 certificate chains, and trusted certificates.
keytool [ commands ]
The keytool command interface has changed in Java SE 6. See the Changes Section for a detailed description. Note that previously defined commands are still supported.
keytool is a key and certificate management utility. It allows users to administer their own public/private key pairs and associated certificates for use in self-authentication (where the user authenticates himself/herself to other users/services) or data integrity and authentication services, using digital signatures. It also allows users to cache the public keys (in the form of certificates) of their communicating peers.
A certificate is a digitally signed statement from one entity (person, company, etc.), saying that the public key (and some other information) of some other entity has a particular value. (See Certificates.) When data is digitally signed, the signature can be verified to check the data integrity and authenticity. Integrity means that the data has not been modified or tampered with, and authenticity means the data indeed comes from whoever claims to have created and signed it.
keytool also enables users to administer secret keys used in symmetric encryption/decryption (e.g. DES).
keytool stores the keys and certificates in a keystore.
The various commands and their options are listed and described below . Note:
keytool -printcert {-file cert_file} {-v}
When specifying a -printcert command, replace cert_file with the actual file name, as in:
keytool -printcert -file VScert.cer
keytoolis equivalent to
keytool -help
Below are the defaults for various option values.
-alias "mykey"
-keyalg
"DSA" (when using -genkeypair)
"DES" (when using -genseckey)
-keysize
1024 (when using -genkeypair)
56 (when using -genseckey and -keyalg is "DES")
168 (when using -genseckey and -keyalg is "DESede")
-validity 90
-keystore the file named .keystore in the user's home directory
-storetype the value of the "keystore.type" property in the security properties file,
which is returned by the static getDefaultType method in java.security.KeyStore
-file stdin if reading, stdout if writing
-protected false
In generating a public/private key pair, the signature algorithm (-sigalg option) is derived from the algorithm of the underlying private key: If the underlying private key is of type "DSA", the -sigalg option defaults to "SHA1withDSA", and if the underlying private key is of type "RSA", -sigalg defaults to "MD5withRSA". Please consult the Java Cryptography Architecture API Specification & Reference @ http://java.sun.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html#AppA for a full list of -keyalg and -sigalg you can choose from.
The -v option can appear for all commands except -help. If it appears, it signifies "verbose" mode; more information will be output.
There is also a -Jjavaoption option that may appear for any command. If it appears, the specified javaoption string is passed through directly to the Java interpreter. This option should not contain any spaces. It is useful for adjusting the execution environment or memory usage. For a list of possible interpreter options, type java -h or java -X at the command line.
These options may appear for all commands operating on a keystore:
If the JKS storetype is used and a keystore file does not yet exist, then certain keytool commands may result in a new keystore file being created. For example, if keytool -genkeypair is invoked and the -keystore option is not specified, the default keystore file named .keystore in the user's home directory will be created if it does not already exist. Similarly, if the -keystore ks_file option is specified but ks_file does not exist, then it will be created
Note that the input stream from the -keystore option is passed to the KeyStore.load method. If NONE is specified as the URL, then a null stream is passed to the KeyStore.load method. NONE should be specified if the KeyStore is not file-based (for example, if it resides on a hardware token device).
storepass must be at least 6 characters long. It must be provided to all commands that access the keystore contents. For such commands, if a -storepass option is not provided at the command line, the user is prompted for it.
When retrieving information from the keystore, the password is optional; if no password is given, the integrity of the retrieved information cannot be checked and a warning is displayed.
Generates a key pair (a public key and associated private key). Wraps the public key into an X.509 v3 self-signed certificate, which is stored as a single-element certificate chain. This certificate chain and the private key are stored in a new keystore entry identified by alias.
keyalg specifies the algorithm to be used to generate the key pair, and keysize specifies the size of each key to be generated. sigalg specifies the algorithm that should be used to sign the self-signed certificate; this algorithm must be compatible with keyalg.
dname specifies the X.500 Distinguished Name to be associated with alias, and is used as the issuer and subject fields in the self-signed certificate. If no distinguished name is provided at the command line, the user will be prompted for one.
keypass is a password used to protect the private key of the generated key pair. If no password is provided, the user is prompted for it. If you press RETURN at the prompt, the key password is set to the same password as that used for the keystore. keypass must be at least 6 characters long.
valDays tells the number of days for which the certificate should be considered valid.
This command was named -genkey in previous releases. This old name is still supported in this release and will be supported in future releases, but for clarify the new name, -genkeypair, is preferred going forward.
Generates a secret key and stores it in a new KeyStore.SecretKeyEntry identified by alias.
keyalg specifies the algorithm to be used to generate the secret key, and keysize specifies the size of the key to be generated. keypass is a password used to protect the secret key. If no password is provided, the user is prompted for it. If you press RETURN at the prompt, the key password is set to the same password as that used for the keystore. keypass must be at least 6 characters long.
Reads the certificate or certificate chain (where the latter is supplied in a PKCS#7 formatted reply) from the file cert_file, and stores it in the keystore entry identified by alias. If no file is given, the certificate or PKCS#7 reply is read from stdin.
keytool can import X.509 v1, v2, and v3 certificates, and PKCS#7 formatted certificate chains consisting of certificates of that type. The data to be imported must be provided either in binary encoding format, or in printable encoding format (also known as Base64 encoding) as defined by the Internet RFC 1421 standard. In the latter case, the encoding must be bounded at the beginning by a string that starts with "-----BEGIN", and bounded at the end by a string that starts with "-----END".
You import a certificate for two reasons:
Which type of import is intended is indicated by the value of the -alias option:
Before adding the certificate to the keystore, keytool tries to verify it by attempting to construct a chain of trust from that certificate to a self-signed certificate (belonging to a root CA), using trusted certificates that are already available in the keystore.
If the -trustcacerts option has been specified, additional certificates are considered for the chain of trust, namely the certificates in a file named "cacerts".
If keytool fails to establish a trust path from the certificate to be imported up to a self-signed certificate (either from the keystore or the "cacerts" file), the certificate information is printed out, and the user is prompted to verify it, e.g., by comparing the displayed certificate fingerprints with the fingerprints obtained from some other (trusted) source of information, which might be the certificate owner himself/herself. Be very careful to ensure the certificate is valid prior to importing it as a "trusted" certificate! -- see WARNING Regarding Importing Trusted Certificates. The user then has the option of aborting the import operation. If the -noprompt option is given, however, there will be no interaction with the user.
When importing a certificate reply, the certificate reply is validated using trusted certificates from the keystore, and optionally using the certificates configured in the "cacerts" keystore file (if the -trustcacerts option was specified).
The methods of determining whether the certificate reply is trusted are described in the following:
If the public key in the certificate reply matches the user's public key already stored with under alias, the old certificate chain is replaced with the new certificate chain in the reply. The old chain can only be replaced if a valid keypass, the password used to protect the private key of the entry, is supplied. If no password is provided, and the private key password is different from the keystore password, the user is prompted for it.
This command was named -import in previous releases. This old name is still supported in this release and will be supported in future releases, but for clarify the new name, -importcert, is preferred going forward.
Imports a single entry or all entries from a source keystore to a destination keystore.
When the srcalias option is provided, the command imports the single entry identified by the alias to the destination keystore. If a destination alias is not provided with destalias, then srcalias is used as the destination alias. If the source entry is protected by a password, srckeypass will be used to recover the entry. If srckeypass is not provided, then keytool will attempt to use srcstorepass to recover the entry. If srcstorepass is either not provided or is incorrect, the user will be prompted for a password. The destination entry will be protected using destkeypass. If destkeypass is not provided, the destination entry will be protected with the source entry password.
If the srcalias option is not provided, then all entries in the source keystore are imported into the destination keystore. Each destination entry will be stored under the alias from the source entry. If the source entry is protected by a password, srcstorepass will be used to recover the entry. If srcstorepass is either not provided or is incorrect, the user will be prompted for a password. If a source keystore entry type is not supported in the destination keystore, or if an error occurs while storing an entry into the destination keystore, the user will be prompted whether to skip the entry and continue, or to quit. The destination entry will be protected with the source entry password.
If the destination alias already exists in the destination keystore, the user is prompted to either overwrite the entry, or to create a new entry under a different alias name.
Note that if -noprompt is provided, the user will not be prompted for a new destination alias. Existing entries will automatically be overwritten with the destination alias name. Finally, entries that can not be imported are automatically skipped and a warning is output.
Generates a Certificate Signing Request (CSR), using the PKCS#10 format.
A CSR is intended to be sent to a certificate authority (CA). The CA will authenticate the certificate requestor (usually off-line) and will return a certificate or certificate chain, used to replace the existing certificate chain (which initially consists of a self-signed certificate) in the keystore.
The private key and X.500 Distinguished Name associated with alias are used to create the PKCS#10 certificate request. In order to access the private key, the appropriate password must be provided, since private keys are protected in the keystore with a password. If keypass is not provided at the command line, and is different from the password used to protect the integrity of the keystore, the user is prompted for it.
sigalg specifies the algorithm that should be used to sign the CSR.
The CSR is stored in the file certreq_file. If no file is given, the CSR is output to stdout.
Use the importcert command to import the response from the CA.
Reads (from the keystore) the certificate associated with alias, and stores it in the file cert_file.
If no file is given, the certificate is output to stdout.
The certificate is by default output in binary encoding, but will instead be output in the printable encoding format, as defined by the Internet RFC 1421 standard, if the -rfc option is specified.
If alias refers to a trusted certificate, that certificate is output. Otherwise, alias refers to a key entry with an associated certificate chain. In that case, the first certificate in the chain is returned. This certificate authenticates the public key of the entity addressed by alias.
This command was named -export in previous releases. This old name is still supported in this release and will be supported in future releases, but for clarify the new name, -exportcert, is preferred going forward.
Prints (to stdout) the contents of the keystore entry identified by alias. If no alias is specified, the contents of the entire keystore are printed.
This command by default prints the MD5 fingerprint of a certificate. If the -v option is specified, the certificate is printed in human-readable format, with additional information such as the owner, issuer, serial number, and any extensions. If the -rfc option is specified, certificate contents are printed using the printable encoding format, as defined by the Internet RFC 1421 standard
You cannot specify both -v and -rfc.
Internet RFC 1421 standard.
Note: This option can be used independently of a keystore.
Changes the password used to protect the integrity of the keystore contents. The new password is new_storepass, which must be at least 6 characters long.
Changes the password under which the private/secret key identified by alias is protected, from old_keypass to new_keypass, which must be at least 6 characters long.
If the -keypass option is not provided at the command line, and the key password is different from the keystore password, the user is prompted for it.
If the -new option is not provided at the command line, the user is prompted for it.
Deletes from the keystore the entry identified by alias. The user is prompted for the alias, if no alias is provided at the command line.
Move an existing keystore entry from the specified alias to a new alias, destalias. If no destination alias is provided, the command will prompt for one. If the original entry is protected with an entry password, the password can be supplied via the "-keypass" option. If no key password is provided, the storepass (if given) will be attempted first. If that attempt fails, the user will be prompted for a password.
Lists the basic commands and their options.
Suppose you want to create a keystore for managing your public/private key pair and certificates from entities you trust.
The first thing you need to do is create a keystore and generate the key pair. You could use a command such as the following:
keytool -genkeypair -dname "cn=Mark Jones, ou=JavaSoft, o=Sun, c=US"
-alias business -keypass kpi135 -keystore /working/mykeystore
-storepass ab987c -validity 180
(Please note: This must be typed as a single line. Multiple lines are used in the examples just for legibility purposes.)
This command creates the keystore named "mykeystore" in the "working" directory (assuming it doesn't already exist), and assigns it the password "ab987c". It generates a public/private key pair for the entity whose "distinguished name" has a common name of "Mark Jones", organizational unit of "JavaSoft", organization of "Sun" and two-letter country code of "US". It uses the default "DSA" key generation algorithm to create the keys, both 1024 bits long.
It creates a self-signed certificate (using the default "SHA1withDSA" signature algorithm) that includes the public key and the distinguished name information. This certificate will be valid for 180 days, and is associated with the private key in a keystore entry referred to by the alias "business". The private key is assigned the password "kpi135".
The command could be significantly shorter if option defaults were accepted. As a matter of fact, no options are required; defaults are used for unspecified options that have default values, and you are prompted for any required values. Thus, you could simply have the following:
keytool -genkeypair
In this case, a keystore entry with alias "mykey" is created, with a newly-generated key pair and a certificate that is valid for 90 days. This entry is placed in the keystore named ".keystore" in your home directory. (The keystore is created if it doesn't already exist.) You will be prompted for the distinguished name information, the keystore password, and the private key password.
The rest of the examples assume you executed the -genkeypair command without options specified, and that you responded to the prompts with values equal to those given in the first -genkeypair command, above (a private key password of "kpi135", etc.)
So far all we've got is a self-signed certificate. A certificate is more likely to be trusted by others if it is signed by a Certification Authority (CA). To get such a signature, you first generate a Certificate Signing Request (CSR), via the following:
keytool -certreq -file MarkJ.csr
This creates a CSR (for the entity identified by the default alias "mykey") and puts the request in the file named "MarkJ.csr". Submit this file to a CA, such as VeriSign, Inc. The CA will authenticate you, the requestor (usually off-line), and then will return a certificate, signed by them, authenticating your public key. (In some cases, they will actually return a chain of certificates, each one authenticating the public key of the signer of the previous certificate in the chain.)
You need to replace your self-signed certificate with a certificate chain, where each certificate in the chain authenticates the public key of the signer of the previous certificate in the chain, up to a "root" CA.
Before you import the certificate reply from a CA, you need one or more "trusted certificates" in your keystore or in the cacerts keystore file (which is described in importcert command):
The "cacerts" keystore file ships with five VeriSign root CA certificates, so you probably won't need to import a VeriSign certificate as a trusted certificate in your keystore. But if you request a signed certificate from a different CA, and a certificate authenticating that CA's public key hasn't been added to "cacerts", you will need to import a certificate from the CA as a "trusted certificate".
A certificate from a CA is usually either self-signed, or signed by another CA (in which case you also need a certificate authenticating that CA's public key). Suppose company ABC, Inc., is a CA, and you obtain a file named "ABCCA.cer" that is purportedly a self-signed certificate from ABC, authenticating that CA's public key.
Be very careful to ensure the certificate is valid prior to importing it as a "trusted" certificate! View it first (using the keytool -printcert command, or the keytool -importcert command without the -noprompt option), and make sure that the displayed certificate fingerprint(s) match the expected ones. You can call the person who sent the certificate, and compare the fingerprint(s) that you see with the ones that they show (or that a secure public key repository shows). Only if the fingerprints are equal is it guaranteed that the certificate has not been replaced in transit with somebody else's (for example, an attacker's) certificate. If such an attack took place, and you did not check the certificate before you imported it, you would end up trusting anything the attacker has signed.
If you trust that the certificate is valid, then you can add it to your keystore via the following:
keytool -importcert -alias abc -file ABCCA.cer
This creates a "trusted certificate" entry in the keystore, with the data from the file "ABCCA.cer", and assigns the alias "abc" to the entry.
Once you've imported a certificate authenticating the public key of the CA you submitted your certificate signing request to (or there's already such a certificate in the "cacerts" file), you can import the certificate reply and thereby replace your self-signed certificate with a certificate chain. This chain is the one returned by the CA in response to your request (if the CA reply is a chain), or one constructed (if the CA reply is a single certificate) using the certificate reply and trusted certificates that are already available in the keystore where you import the reply or in the "cacerts" keystore file.
For example, suppose you sent your certificate signing request to VeriSign. You can then import the reply via the following, which assumes the returned certificate is named "VSMarkJ.cer":
keytool -importcert -trustcacerts -file VSMarkJ.cer
Suppose you have used the jarsigner @ http://java.sun.com/javase/6/docs/tooldocs/solaris/jarsigner.html tool to sign a Java ARchive (JAR) file. Clients that want to use the file will want to authenticate your signature.
One way they can do this is by first importing your public key certificate into their keystore as a "trusted" entry. You can export the certificate and supply it to your clients. As an example, you can copy your certificate to a file named MJ.cer via the following, assuming the entry is aliased by "mykey":
keytool -exportcert -alias mykey -file MJ.cer
Given that certificate, and the signed JAR file, a client can use the jarsigner tool to authenticate your signature.
The command "importkeystore" is used to import an entire keystore into another keystore, which means all entries from the source keystore, including keys and certificates, are all imported to the destination keystore within a single command. You can use this command to import entries from a different type of keystore. During the import, all new entries in the destination keystore will have the same alias names and protection passwords (for secret keys and private keys). If keytool has difficulties recover the private keys or secret keys from the source keystore, it will prompt you for a password. If it detects alias duplication, it will ask you for a new one, you can specify a new alias or simply allow keytool to overwrite the existing one.
For example, to import entries from a normal JKS type keystore key.jks into a PKCS #11 type hardware based keystore, you can use the command:
keytool -importkeystore
-srckeystore key.jks -destkeystore NONE
-srcstoretype JKS -deststoretype PKCS11
-srcstorepass changeit -deststorepass topsecret
The importkeystore command can also be used to import a single entry from a source keystore to a destination keystore. In this case, besides the options you see in the above example, you need to specify the alias you want to import. With the srcalias option given, you can also specify the desination alias name in the command line, as well as protection password for a secret/private key and the destination protection password you want. In this way, you can issue a keytool command that will never ask you a question. This makes it very convenient to include a keytool command into a script file, like this:
keytool -importkeystore
-srckeystore key.jks -destkeystore NONE
-srcstoretype JKS -deststoretype PKCS11
-srcstorepass changeit -deststorepass topsecret
-srcalias myprivatekey -destalias myoldprivatekey
-srckeypass oldkeypass -destkeypass mynewkeypass
-noprompt
A keystore is a storage facility for cryptographic keys and certificates.
Keystores may have different types of entries. The two most applicable entry types for keytool include:
All keystore entries (key and trusted certificate entries) are accessed via unique aliases.
An alias is specified when you add an entity to the keystore using the -genseckey command to generate a secret key, -genkeypair command to generate a key pair (public and private key) or the -importcert command to add a certificate or certificate chain to the list of trusted certificates. Subsequent keytool commands must use this same alias to refer to the entity.
For example, suppose you use the alias duke to generate a new public/private key pair and wrap the public key into a self-signed certificate (see Certificate Chains) via the following command:
keytool -genkeypair -alias duke -keypass dukekeypasswd
This specifies an inital password of "dukekeypasswd" required by subsequent commands to access the private key assocated with the alias duke. If you later want to change duke's private key password, you use a command like the following:
keytool -keypasswd -alias duke -keypass dukekeypasswd -new newpass
This changes the password from "dukekeypasswd" to "newpass".
Please note: A password should not actually be specified on a command line or in a script unless it is for testing purposes, or you are on a secure system. If you don't specify a required password option on a command line, you will be prompted for it.
Currently, two command-line tools (keytool and jarsigner) and a GUI-based tool named Policy Tool make use of keystore implementations. Since KeyStore is publicly available, users can write additional security applications that use it.
There is a built-in default implementation, provided by Sun Microsystems. It implements the keystore as a file, utilizing a proprietary keystore type (format) named "JKS". It protects each private key with its individual password, and also protects the integrity of the entire keystore with a (possibly different) password.
Keystore implementations are provider-based. More specifically, the application interfaces supplied by KeyStore are implemented in terms of a "Service Provider Interface" (SPI). That is, there is a corresponding abstract KeystoreSpi class, also in the java.security package, which defines the Service Provider Interface methods that "providers" must implement. (The term "provider" refers to a package or a set of packages that supply a concrete implementation of a subset of services that can be accessed by the Java Security API.) Thus, to provide a keystore implementation, clients must implement a "provider" and supply a KeystoreSpi subclass implementation, as described in How to Implement a Provider for the Java Cryptography Architecture.
Applications can choose different types of keystore implementations from different providers, using the "getInstance" factory method supplied in the KeyStore class. A keystore type defines the storage and data format of the keystore information, and the algorithms used to protect private/secret keys in the keystore and the integrity of the keystore itself. Keystore implementations of different types are not compatible.
keytool works on any file-based keystore implementation. (It treats the keytore location that is passed to it at the command line as a filename and converts it to a FileInputStream, from which it loads the keystore information.) The jarsigner and policytool tools, on the other hand, can read a keystore from any location that can be specified using a URL.
For keytool and jarsigner, you can specify a keystore type at the command line, via the -storetype option. For Policy Tool, you can specify a keystore type via the "Keystore" menu.
If you don't explicitly specify a keystore type, the tools choose a keystore implementation based simply on the value of the keystore.type property specified in the security properties file. The security properties file is called java.security, and it resides in the security properties directory, java.home/lib/security, where java.home is the runtime environment's directory (the jre directory in the SDK or the top-level directory of the Java 2 Runtime Environment).
Each tool gets the keystore.type value and then examines all the currently-installed providers until it finds one that implements keystores of that type. It then uses the keystore implementation from that provider.
The KeyStore class defines a static method named getDefaultType that lets applications and applets retrieve the value of the keystore.type property. The following line of code creates an instance of the default keystore type (as specified in the keystore.type property):
KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
The default keystore type is "jks" (the proprietary type of the keystore implementation provided by Sun). This is specified by the following line in the security properties file:
keystore.type=jks
To have the tools utilize a keystore implementation other than the default, you can change that line to specify a different keystore type.
For example, if you have a provider package that supplies a keystore implementation for a keystore type called "pkcs12", change the line to
keystore.type=pkcs12
Note: case doesn't matter in keystore type designations. For example, "JKS" would be considered the same as "jks".
A certificate (also known as a public-key certificate) is a digitally signed statement from one entity (the issuer), saying that the public key (and some other information) of another entity (the subject) has some specific value.
Basically, public key cryptography requires access to users' public keys. In a large-scale networked environment it is impossible to guarantee that prior relationships between communicating entities have been established or that a trusted repository exists with all used public keys. Certificates were invented as a solution to this public key distribution problem. Now a Certification Authority (CA) can act as a trusted third party. CAs are entities (for example, businesses) that are trusted to sign (issue) certificates for other entities. It is assumed that CAs will only create valid and reliable certificates, as they are bound by legal agreements. There are many public Certification Authorities, such as VeriSign @ http://www.verisign.com/, Thawte @ http://www.thawte.com/, Entrust @ http://www.entrust.com/, and so on. You can also run your own Certification Authority using products such as the Netscape/Microsoft Certificate Servers or the Entrust CA product for your organization.
Using keytool, it is possible to display, import, and export certificates. It is also possible to generate self-signed certificates.
keytool currently handles X.509 certificates.
All X.509 certificates have the following data, in addition to the signature:
X.509 Version 1 has been available since 1988, is widely deployed, and is the most generic.
X.509 Version 2 introduced the concept of subject and issuer unique identifiers to handle the possibility of reuse of subject and/or issuer names over time. Most certificate profile documents strongly recommend that names not be reused, and that certificates should not make use of unique identifiers. Version 2 certificates are not widely used.
X.509 Version 3 is the most recent (1996) and supports the notion of extensions, whereby anyone can define an extension and include it in the certificate. Some common extensions in use today are: KeyUsage (limits the use of the keys to particular purposes such as "signing-only") and AlternativeNames (allows other identities to also be associated with this public key, e.g. DNS names, Email addresses, IP addresses). Extensions can be marked critical to indicate that the extension should be checked and enforced/used. For example, if a certificate has the KeyUsage extension marked critical and set to "keyCertSign" then if this certificate is presented during SSL communication, it should be rejected, as the certificate extension indicates that the associated private key should only be used for signing certificates and not for SSL use.
CN=Java Duke, OU=Java Software Division, O=Sun Microsystems Inc, C=US
(These refer to the subject's Common Name, Organizational Unit, Organization, and Country.)
keytool can create and manage keystore "key" entries that each contain a private key and an associated certificate "chain". The first certificate in the chain contains the public key corresponding to the private key.
When keys are first generated (see the -genkeypair command), the chain starts off containing a single element, a self-signed certificate. A self-signed certificate is one for which the issuer (signer) is the same as the subject (the entity whose public key is being authenticated by the certificate). Whenever the -genkeypair command is called to generate a new public/private key pair, it also wraps the public key into a self-signed certificate.
Later, after a Certificate Signing Request (CSR) has been generated (see the -certreq command) and sent to a Certification Authority (CA), the response from the CA is imported (see -importcert), and the self-signed certificate is replaced by a chain of certificates. At the bottom of the chain is the certificate (reply) issued by the CA authenticating the subject's public key. The next certificate in the chain is one that authenticates the CA's public key.
In many cases, this is a self-signed certificate (that is, a certificate from the CA authenticating its own public key) and the last certificate in the chain. In other cases, the CA may return a chain of certificates. In this case, the bottom certificate in the chain is the same (a certificate signed by the CA, authenticating the public key of the key entry), but the second certificate in the chain is a certificate signed by a different CA, authenticating the public key of the CA you sent the CSR to. Then, the next certificate in the chain will be a certificate authenticating the second CA's key, and so on, until a self-signed "root" certificate is reached. Each certificate in the chain (after the first) thus authenticates the public key of the signer of the previous certificate in the chain.
Many CAs only return the issued certificate, with no supporting chain, especially when there is a flat hierarchy (no intermediates CAs). In this case, the certificate chain must be established from trusted certificate information already stored in the keystore.
A different reply format (defined by the PKCS#7 standard) also includes the supporting certificate chain, in addition to the issued certificate. Both reply formats can be handled by keytool.
The top-level (root) CA certificate is self-signed. However, the trust into the root's public key does not come from the root certificate itself (anybody could generate a self-signed certificate with the distinguished name of say, the VeriSign root CA!), but from other sources like a newspaper. The root CA public key is widely known. The only reason it is stored in a certificate is because this is the format understood by most tools, so the certificate in this case is only used as a "vehicle" to transport the root CA's public key. Before you add the root CA certificate to your keystore, you should view it (using the -printcert option) and compare the displayed fingerprint with the well-known fingerprint (obtained from a newspaper, the root CA's webpage, etc.).
A certificates file named "cacerts" resides in the security properties directory, java.home/lib/security, where java.home is the runtime environment's directory (the jre directory in the SDK or the top-level directory of the Java 2 Runtime Environment).
The "cacerts" file represents a system-wide keystore with CA certificates. System administrators can configure and manage that file using keytool, specifying "jks" as the keystore type. The "cacerts" keystore file ships with several root CA certificates with the following aliases and X.500 owner distinguished names:
The initial password of the "cacerts" keystore file is "changeit". System administrators should change that password and the default access permission of that file upon installing the SDK.
IMPORTANT: Verify Your cacerts File
Since you trust the CAs in the cacerts file as entities for signing and issuing certificates to other entities, you must manage the cacerts file carefully. The cacerts file should contain only certificates of the CAs you trust. It is your responsibility to verify the trusted root CA certificates bundled in the cacerts file and make your own trust decisions. To remove an untrusted CA certificate from the cacerts file, use the delete option of the keytool command. You can find the cacerts file in the JRE installation directory. Contact your system administrator if you do not have permission to edit this file.
Certificates are often stored using the printable encoding format defined by the Internet RFC 1421 standard, instead of their binary encoding. This certificate format, also known as "Base 64 encoding", facilitates exporting certificates to other applications by email or through some other mechanism.
Certificates read by the -importcert and -printcert commands can be in either this format or binary encoded.
The -exportcert command by default outputs a certificate in binary encoding, but will instead output a certificate in the printable encoding format, if the -rfc option is specified.
The -list command by default prints the MD5 fingerprint of a certificate. If the -v option is specified, the certificate is printed in human-readable format, while if the -rfc option is specified, the certificate is output in the printable encoding format.
In its printable encoding format, the encoded certificate is bounded at the beginning by
-----BEGIN CERTIFICATE-----
and at the end by
-----END CERTIFICATE-----
X.500 Distinguished Names are used to identify entities, such as those which are named by the subject and issuer (signer) fields of X.509 certificates. keytool supports the following subparts:
When supplying a distinguished name string as the value of a -dname option, as for the -genkeypair command, the string must be in the following format:
CN=cName, OU=orgUnit, O=org, L=city, S=state, C=countryCode
where all the italicized items represent actual values and the above keywords are abbreviations for the following:
CN=commonName
OU=organizationUnit
O=organizationName
L=localityName
S=stateName
C=country
A sample distinguished name string is
CN=Mark Smith, OU=JavaSoft, O=Sun, L=Cupertino, S=California, C=US
and a sample command using such a string is
keytool -genkeypair -dname "CN=Mark Smith, OU=JavaSoft, O=Sun, L=Cupertino, S=California, C=US" -alias mark
Case does not matter for the keyword abbreviations. For example, "CN", "cn", and "Cn" are all treated the same.
Order matters; each subcomponent must appear in the designated order. However, it is not necessary to have all the subcomponents. You may use a subset, for example:
CN=Steve Meier, OU=SunSoft, O=Sun, C=US
If a distinguished name string value contains a comma, the comma must be escaped by a "\" character when you specify the string on a command line, as in
cn=peter schuster, o=Sun Microsystems\, Inc., o=sun, c=us
It is never necessary to specify a distinguished name string on a command line. If it is needed for a command, but not supplied on the command line, the user is prompted for each of the subcomponents. In this case, a comma does not need to be escaped by a "\".
IMPORTANT: Be sure to check a certificate very carefully before importing it as a trusted certificate!
View it first (using the -printcert command, or the -importcert command without the -noprompt option), and make sure that the displayed certificate fingerprint(s) match the expected ones. For example, suppose someone sends or emails you a certificate, and you put it in a file named /tmp/cert. Before you consider adding the certificate to your list of trusted certificates, you can execute a -printcert command to view its fingerprints, as in
keytool -printcert -file /tmp/cert
Owner: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
Issuer: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
Serial Number: 59092b34
Valid from: Thu Sep 25 18:01:13 PDT 1997 until: Wed Dec 24 17:01:13 PST 1997
Certificate Fingerprints:
MD5: 11:81:AD:92:C8:E5:0E:A2:01:2E:D4:7A:D7:5F:07:6F
SHA1: 20:B6:17:FA:EF:E5:55:8A:D0:71:1F:E8:D6:9D:C0:37:13:0E:5E:FE
Then call or otherwise contact the person who sent the certificate, and compare the fingerprint(s) that you see with the ones that they show. Only if the fingerprints are equal is it guaranteed that the certificate has not been replaced in transit with somebody else's (for example, an attacker's) certificate. If such an attack took place, and you did not check the certificate before you imported it, you would end up trusting anything the attacker has signed (for example, a JAR file with malicious class files inside).
Note: it is not required that you execute a -printcert command prior to importing a certificate, since before adding a certificate to the list of trusted certificates in the keystore, the -importcert command prints out the certificate information and prompts you to verify it. You then have the option of aborting the import operation. Note, however, this is only the case if you invoke the -importcert command without the -noprompt option. If the -noprompt option is given, there is no interaction with the user.
Most commands operating on a keystore require the store password. Some commands require a private/secret key password.
Passwords can be specified on the command line (in the -storepass and -keypass options, respectively). However, a password should not be specified on a command line or in a script unless it is for testing purposes, or you are on a secure system.
If you don't specify a required password option on a command line, you will be prompted for it.
The command interface for keytool changed in Java SE 6.
keytool no longer displays password input when entered by users. Since password input can no longer be viewed when entered, users will be prompted to re-enter passwords any time a password is being set or changed (for example, when setting the initial keystore password, or when changing a key password).
Some commands have simply been renamed, and other commands deemed obsolete are no longer listed in this document. All previous commands (both renamed and obsolete) are still supported in this release and will continue to be supported in future releases. The following summarizes all of the changes made to the keytool command interface:
Renamed commands:
Commands deemed obsolete and no longer documented: