#Java jar file exercise zip#
In addition, APIs allow applications to obtain the timestamp information.Īt this time, the jarsigner command can only sign JAR files created by the jar command or zip files. The jarsigner command can generate signatures that include a time stamp that enables a systems or deployer to check whether the JAR file was signed while the signing certificate was still valid. The jarsigner command can verify the digital signature of the signed JAR file using the certificate inside it (in its signature block file). The signed JAR file contains, among other things, a copy of the certificate from the keystore for the public key corresponding to the private key used to sign the file. The jarsigner command uses an entity's private key to generate a signature. The keytool command is used to create and administer keystores. A keystore is a database of private keys and their associated X.509 certificate chains that authenticate the corresponding public keys. The jarsigner command uses key and certificate information from a keystore to generate digital signatures for JAR files. A certificate is a digitally signed statement from one entity that says that the public key of another entity has a particular value. To generate an entity's signature for a file, the entity must first have a public/private key pair associated with it and one or more certificates that authenticate its public key. If the data is changed, then the signature can't be verified as authentic.
It is a function of the data signed and thus can't be claimed to be the signature for other data as well. It can't be forged, assuming the private key is kept secret. Its authenticity can be verified by a computation that uses the public key corresponding to the private key used to generate the signature. Similar to a handwritten signature, a digital signature has many useful characteristics:
#Java jar file exercise zip file#
(Technically, any ZIP file can also be considered a JAR file, although when created by the jar command or processed by the jarsigner command, JAR files also contain a META-INF/MANIFEST.MF file.)Ī digital signature is a string of bits that is computed from some data (the data being signed) and the private key of an entity (a person, company, and so on). A tool named jar enables developers to produce JAR files. The JAR feature enables the packaging of class files, images, sounds, and other digital data in a single file for faster and easier distribution. To verify the signatures and integrity of signed JAR files. The aliases are defined in the keystore specified by -keystore or the default keystore. If you also specified the -strict option, and the jarsigner command detected severe warnings, the message, "jar signed, with signer errors" is displayed. If you also specify the -strict option, and the jarsigner command detects severe warnings, the message, "jar verified, with signer errors" is displayed. When the -verify option is specified, the jarsigner command checks that the certificate used to verify each signed entry in the JAR file matches one of the keystore aliases. The -verify option can take zero or more keystore alias names after the JAR file name. Jarsigner -verify _options_ _jar-file_ _alias_. Synopsis jarsigner _options_ _jar-file_ _alias_
#Java jar file exercise archive#
Jarsigner - sign and verify Java Archive (JAR) files
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