Now, only the person you intend the message for can decrypt it since only they have access to their private key. Why is this important? Some services, take the Android Play Store for example, require you to sign your jar apk before submitting it to add a layer of security. In the case of jars and commit messages, the code you are signing is not actually encrypted as would be the case if you're trying to send a private email or packaging an iOS app.
Thus, no one else can generate the same signature as you save in the extremely unlikely event of a collision. By attaching your signature to the code, you are saying that you are responsible for it.
If I somehow got a hold of the Facebook developer account for the Play Store, I can't just upload a new Facebook app update that sends me s of millions of users' information because I would be unable forge Facebook's signature without their heavily protected private key. It's the same idea for commit messages. You are keeping a record of who does what.
You can hold people responsible and on top of that prevent unauthorized people from committing code. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Learn more. Why do we sign a. The Jarsigner tool will prompt you for the passwords for the keystore and alias. This basic form of the command assumes that the keystore to be used is in a file named. It will create signature and signature block files with names x. SF and x. DSA respectively, where x is the first eight letters of the alias, all converted to upper case. In practice, you may want to use this command in conjunction with one or more of these options, which must precede the jar-file pathname: Option Description -keystore url Specifies a keystore to be used if you don't want to use the.
In a Java 2 environment, Derby can detect digital signatures on jar files. When attempting to load a class from a signed jar file stored in the database, Derby will verify the validity of the signature.
When loading classes from an application jar file in a Java 2 environment, Derby behaves as follows:. About these manuals. About this web site. Items in italics option values represent the actual values that must be supplied. The -keystore , -storepass , -keypass , -sigfile , and -signedjar options are only relevant when signing a JAR file, not when verifying a signed JAR file.
Similarly, an alias is only specified on the command line when signing a JAR file. This defaults to the file. A keystore is required when signing, so you must explicitly specify one if the default keystore does not exist or you want to use one other than the default. A keystore is not required when verifying, but if one is specified, or the default exists, and the -verbose option was also specified, additional information is output regarding whether or not any of the certificates used to verify the JAR file are contained in that keystore.
Note: the -keystore argument can actually be a file name and path specification rather than a URL, in which case it will be treated the same as a "file:" URL. The default keystore type is the one that is specified as the value of the "keystore.
If none has been specified, keytool and jarsigner will prompt for the token PIN. If the token has a protected authentication path such as a dedicated PIN-pad or a biometric reader , then the -protected option must be specified and no password options can be specified. This is only needed when signing not verifying a JAR file. In that case, if a -storepass option is not provided at the command line, the user is prompted for the password.
Note: The password shouldn't be specified on the command line or in a script unless it is for testing purposes, or you are on a secure system. Also, when typing in a password at the password prompt, the password is echoed displayed exactly as typed , so be careful not to type it in front of anyone. The password is required when using jarsigner to sign a JAR file. If no password is provided on the command line, and the required password is different from the store password, the user is prompted for it.
DSA files. That is, only letters, numbers, underscore, and hyphen characters are allowed. Note: All lowercase characters will be converted to uppercase for the.
DSA file names. If no name is specified on the command line, the name used is the same as the input JAR file name the name of the JAR file to be signed ; in other words, that file is overwritten with the signed JAR file. If the verification is successful, "jar verified" will be displayed. This information includes the name of the type of certificate stored in the.
DSA file that certifies the signer's public key if the certificate is an X. XCertificate : the distinguished name of the signer The keystore is also examined. If no keystore value is specified on the command line, the default keystore file if any will be checked.
If the public key certificate for a signer matches an entry in the keystore, then the following information will also be displayed: in parentheses, the alias name for the keystore entry for that signer.
If the signer actually comes from a JDK 1. DSA signature block file generated when a JAR file was signed used to include a complete encoded copy of the. SF file signature file also generated. This behavior has been changed. To reduce the overall size of the output JAR file, the. DSA file by default doesn't contain a copy of the. SF file anymore. But if -internalsf appears on the command line, the old behavior is utilized.
This option is mainly useful for testing; in practice, it should not be used, since doing so eliminates a useful optimization. SF file signature file generated when a JAR file is signed does not include a header containing a hash of the whole manifest file.
It just contains information and hashes related to each individual source file included in the JAR file, as described in The Signature. By default, this header is added, as an optimization. When the header is present, then whenever the JAR file is verified, the verification can first check to see whether or not the hash in the header indeed matches the hash of the whole manifest file.
If so, verification proceeds to the next step. If not, it is necessary to do a less optimized verification that the hash in each source file information section in the.
SF file equals the hash of its corresponding section in the manifest file. Used in conjunction with the -providerArg ConfigFilePath option, keytool and jarsigner will install the provider dynamically where ConfigFilePath is the path to the token configuration file. The argument to this option is the name of the provider.
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.
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