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If the underlying private key is of type "DSA", the -sigalg option defaults to "SHA1withDSA"

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If the underlying private key is of type "RSA", the -sigalg option defaults to "SHA256withRSA".

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If the underlying private key is of type "EC", the -sigalg option defaults to "SHA256withECDSA".

-storetype storetype

This qualifier specifies the type of keystore to be instantiated.

-keystore keystore

The keystore location.

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[:env|:file] argument

The password which is used to protect the integrity of the keystore.

If the modifier env or file is not specified, then the password has the value argument, which must be at least 6 characters long. Otherwise, the password is retrieved as follows:

Note: All other options that require passwords, such as -keypass, -srckeypass, -destkeypass -srcstorepass, and -deststorepass, accept the env and file modifiers. (Remember to separate the password option and the modifier with a colon, (:).)

The password 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.

-providerName provider_name

Used to identify a cryptographic service provider's name when listed in the security properties file.

-providerClass provider_class_name

Used to specify the name of cryptographic service provider's master class file when the service provider is not listed in the security properties file.

-providerArg provider_arg

Used in conjunction with -providerClass. Represents an optional string input argument for the constructor of provider_class_name.

-protected

Either true or false. This value should be specified as true if a password must be given via a protected authentication path such as a dedicated PIN reader.

Note: Since there are two keystores involved in -importkeystore command, two options, namely, -srcprotected and -destprotected are provided for the source keystore and the destination keystore respectively.

-ext {name{:critical}{=value}}

Denotes an X.509 certificate extension. The option can be used in -genkeypair and -gencert to embed extensions into the certificate generated, or in -certreq to show what extensions are requested in the certificate request. The option can appear multiple times. name can be a supported extension name (see below) or an arbitrary OID number. value, if provided, denotes the parameter for the extension; if omitted, denotes the default value (if defined) of the extension or the extension requires no parameter. The :critical modifier, if provided, means the extension's isCritical attribute is true; otherwise, false. You may use :c in place of :critical.

-gencert {-rfc} {-infile infile} {-outfile outfile} {-alias alias} {-sigalg sigalg} {-dname dname} {-startdate startdate {-ext ext}* {-validity valDays} [-keypass keypass] {-keystore keystore} [-storepass storepass] {-storetype storetype} {-providername provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

Generates a certificate as a response to a certificate request file (which can be created by the keytool -certreq command). The command reads the request from infile (if omitted, from the standard input), signs it using alias's private key, and output the X.509 certificate into outfile (if omitted, to the standard output). If -rfc is specified, output format is BASE64-encoded PEM; otherwise, a binary DER is created.

sigalg specifies the algorithm that should be used to sign the certificate. startdate is the start time/date that the certificate is valid. valDays tells the number of days for which the certificate should be considered valid.

If dname is provided, it's used as the subject of the generated certificate. Otherwise, the one from the certificate request is used.

ext shows what X.509 extensions will be embedded in the certificate. Read Common Options for the grammar of -ext.

The -gencert command enables you to create certificate chains. The following example creates a certificate, e1, that contains three certificates in its certificate chain.

The following commands creates four key pairs named ca, ca1, ca2, and e1:

keytool -alias ca -dname CN=CA -genkeypair
keytool -alias ca1 -dname CN=CA -genkeypair
keytool -alias ca2 -dname CN=CA -genkeypair
keytool -alias e1 -dname CN=E1 -genkeypair

The following two commands create a chain of signed certificates; ca signs ca1 and ca1 signs ca2, all of which are self-issued:

keytool -alias ca1 -certreq | keytool -alias ca -gencert -ext san=dns:ca1 | keytool -alias ca1 -importcert
keytool -alias ca2 -certreq | $KT -alias ca1 -gencert -ext san=dns:ca2 | $KT -alias ca2 -importcert

The following command creates the certificate e1 and stores it in the file e1.cert, which is signed by ca2. As a result, e1 should contain ca, ca1, and ca2 in its certificate chain:

keytool -alias e1 -certreq | keytool -alias ca2 -gencert > e1.cert

-genkeypair {-alias alias} {-keyalg keyalg} {-keysize keysize} {-sigalg sigalg} [-dname dname] [-keypass keypass] {-startdate value} {-ext ext}* {-validity valDays} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

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.

startdate specifies the issue time of the certificate, also known as the "Not Before" value of the X.509 certificate's Validity field.

The option value can be set in one of these two forms:

With the first form, the issue time is shifted by the specified value from the current time. The value is a concatenation of a sequence of sub values. Inside each sub value, the plus sign ("+") means shifting forward, and the minus sign ("-") means shifting backward. The time to be shifted is nnn units of years, months, days, hours, minutes, or seconds (denoted by a single character of "y", "m", "d", "H", "M", or "S" respectively). The exact value of the issue time is calculated using the java.util.GregorianCalendar.add(int field, int amount) method on each sub value, from left to right. For example, by specifying "-startdate -1y+1m-1d", the issue time will be:

   Calendar c = new GregorianCalendar();


   c.add(Calendar.YEAR, -1);


   c.add(Calendar.MONTH, 1);


   c.add(Calendar.DATE, -1);


   return c.getTime()

With the second form, the user sets the exact issue time in two parts, year/month/day and hour:minute:second (using the local time zone). The user may provide only one part, which means the other part is the same as the current date (or time). User must provide the exact number of digits as shown in the format definition (padding with 0 if shorter). When both the date and time are provided, there is one (and only one) space character between the two parts. The hour should always be provided in 24 hour format.

When the option is not provided, the start date is the current time. The option can be provided at most once.

valDays specifies the number of days (starting at the date specified by -startdate, or the current date if -startdate is not specified) 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 clarity the new name, -genkeypair, is preferred going forward.

-genseckey {-alias alias} {-keyalg keyalg} {-keysize keysize} [-keypass keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

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.

-importcert {-alias alias} {-file cert_file} [-keypass keypass] {-noprompt} {-trustcacerts} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

Reads the certificate or certificate chain (where the latter is supplied in a PKCS#7 formatted reply or a sequence of X.509 certificates) from the file cert_file, and stores it in the keystore entry identified by alias. If no file is given, the certificate or certificate chain 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. Importing a Certificate Reply

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.

-importkeystore -srckeystore srckeystore -destkeystore destkeystore {-srcstoretype srcstoretype} {-deststoretype deststoretype} [-srcstorepass srcstorepass] [-deststorepass deststorepass] {-srcprotected} {-destprotected} {-srcalias srcalias {-destalias destalias} [-srckeypass srckeypass] [-destkeypass destkeypass] } {-noprompt} {-srcProviderName src_provider_name} {-destProviderName dest_provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

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.

-printcertreq {-file file}

Prints the content of a PKCS #10 format certificate request, which can be generated by the keytool -certreq command. The command reads the request from file; if omitted, from the standard input.

-certreq {-alias alias} {-dname dname} {-sigalg sigalg} {-file certreq_file} [-keypass keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

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 associated with alias is 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. If dname is provided, it's used as the subject in the CSR. Otherwise, the X.500 Distinguished Name associated with alias is used.

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.

-exportcert {-alias alias} {-file cert_file} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-rfc} {-v} {-protected} {-Jjavaoption}

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.

-list {-alias alias} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v | -rfc} {-protected} {-Jjavaoption}

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 SHA1 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.

-printcert {-file cert_file | -sslserver host[:port]} {-jarfile JAR_file {-rfc} {-v} {-Jjavaoption}

Reads the certificate from the file cert_file, the SSL server located at host:port, or the signed JAR file JAR_file (with the option -jarfile and prints its contents in a human-readable format. When no port is specified, the standard HTTPS port 443 is assumed. Note that -sslserver and -file options cannot be provided at the same time. Otherwise, an error is reported. If neither option is given, the certificate is read from stdin.

If -rfc is specified, keytool prints the certificate in PEM mode as defined by the Internet RFC 1421 standard.

If the certificate is read from a file or stdin, it may be either binary encoded or in printable encoding format, as defined by the Internet RFC 1421 standard

If the SSL server is behind a firewall, -J-Dhttps.proxyHost=proxyhost and -J-Dhttps.proxyPort=proxyport can be specified on the command line for proxy tunneling. See the JSSE Reference Guide @
http://docs.oracle.com/javase/7/docs/technotes/guides/security/jsse/JSSERefGuide.html for more information.

Note: This option can be used independently of a keystore.

-printcrl -file crl_ {-v}

Reads the certificate revocation list (CRL) from the file crl_file.

A Certificate Revocation List (CRL) is a list of digital certificates which have been revoked by the Certificate Authority (CA) that issued them. The CA generates crl_file.

Note: This option can be used independently of a keystore.

-storepasswd [-new new_storepass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-Jjavaoption}

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.

-keypasswd {-alias alias} [-keypass old_keypass] [-new new_keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-Jjavaoption}

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.

-delete [-alias alias] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

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.

-changealias {-alias alias} [-destalias destalias] [-keypass keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-providerName provider_name} {-providerClass provider_class_name {-providerArg provider_arg}} {-v} {-protected} {-Jjavaoption}

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.

-help

Lists the basic commands and their options.

For more information about a specific command, enter the following, where command_name is the name of the command:

    keytool -command_name -help

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If the certificate reply is a certificate chain, you just need the top certificate of the chain (that is, the "root" CA certificate authenticating that CA's public key).

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If the certificate reply is a single certificate, you need a certificate for the issuing CA (the one that signed it), and if that certificate is not self-signed, you need a certificate for its signer, and so on, up to a self-signed "root" CA certificate.

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KeyStore Entries

Keystores may have different types of entries. The two most applicable entry types for keytool include:

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KeyStore Aliases

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 initial password of "dukekeypasswd" required by subsequent commands to access the private key associated 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.

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KeyStore Implementation

The KeyStore class provided in the java.security package supplies well-defined interfaces to access and modify the information in a keystore. It is possible for there to be multiple different concrete implementations, where each implementation is that for a particular type of keystore.

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 Oracle. 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 @
http://docs.oracle.com/javase/7/docs/technotes/guides/security/crypto/HowToImplAProvider.html.

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 keystore 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 Oracle). 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".

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Certificate Terms

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 Microsoft Certificate Server 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.

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X.509 Certificates

The X.509 standard defines what information can go into a certificate, and describes how to write it down (the data format). All the data in a certificate is encoded using two related standards called ASN.1/DER. Abstract Syntax Notation 1 describes data. The Definite Encoding Rules describe a single way to store and transfer that data.

All X.509 certificates have the following data, in addition to the signature:

    CN=Java Duke, OU=Java Software Division, O=Oracle Corporation, C=US

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Certificate Chains

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 Web page, etc.).

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The cacerts Certificates File

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 a default set of root CA certificates; list them with the following command:

keytool -list -keystore java.home/lib/security/cacerts

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.

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The Internet RFC 1421 Certificate Encoding Standard

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 SHA1 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-----

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commonName - common name of a person, e.g., "Susan Jones"

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organizationUnit - small organization (e.g., department or division) name, e.g., "Purchasing"

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organizationName - large organization name, e.g., "ABCSystems, Inc."

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localityName - locality (city) name, e.g., "Palo Alto"

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stateName - state or province name, e.g., "California"

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country - two-letter country code, e.g., "CH"