jdk.security.MessageDigest — clojure-interop/java.security 1.0.5

This MessageDigest class provides applications the functionality of a message digest algorithm, such as SHA-1 or SHA-256. Message digests are secure one-way hash functions that take arbitrary-sized data and output a fixed-length hash value.

A MessageDigest object starts out initialized. The data is processed through it using the update methods. At any point reset can be called to reset the digest. Once all the data to be updated has been updated, one of the digest methods should be called to complete the hash computation.

The digest method can be called once for a given number of updates. After digest has been called, the MessageDigest object is reset to its initialized state.

Implementations are free to implement the Cloneable interface. Client applications can test cloneability by attempting cloning and catching the CloneNotSupportedException:

MessageDigest md = MessageDigest.getInstance("SHA-256");

try { md.update(toChapter1); MessageDigest tc1 = md.clone(); byte[] toChapter1Digest = tc1.digest(); md.update(toChapter2); ...etc. } catch (CloneNotSupportedException cnse) { throw new DigestException("couldn't make digest of partial content"); }

Note that if a given implementation is not cloneable, it is still possible to compute intermediate digests by instantiating several instances, if the number of digests is known in advance.

Note that this class is abstract and extends from MessageDigestSpi for historical reasons. Application developers should only take notice of the methods defined in this MessageDigest class; all the methods in the superclass are intended for cryptographic service providers who wish to supply their own implementations of message digest algorithms.

Every implementation of the Java platform is required to support the following standard MessageDigest algorithms:

MD5 SHA-1 SHA-256

These algorithms are described in the MessageDigest section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.

*equal? clj

(*equal? digesta digestb)

Compares two digests for equality. Does a simple byte compare.

digesta - one of the digests to compare. - byte[] digestb - the other digest to compare. - byte[]

returns: true if the digests are equal, false otherwise. - boolean

*get-instance clj

(*get-instance algorithm)

(*get-instance algorithm provider)

Returns a MessageDigest object that implements the specified digest algorithm.

A new MessageDigest object encapsulating the MessageDigestSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

algorithm - the name of the algorithm requested. See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names. - java.lang.String provider - the name of the provider. - java.lang.String

returns: a MessageDigest object that implements the specified algorithm. - java.security.MessageDigest

throws: java.security.NoSuchAlgorithmException - if a MessageDigestSpi implementation for the specified algorithm is not available from the specified provider.

clone clj

(clone this)

Returns a clone if the implementation is cloneable.

returns: a clone if the implementation is cloneable. - java.lang.Object

throws: java.lang.CloneNotSupportedException - if this is called on an implementation that does not support Cloneable.

digest clj

(digest this)

(digest this input)

(digest this buf offset len)

Completes the hash computation by performing final operations such as padding. The digest is reset after this call is made.

buf - output buffer for the computed digest - byte[] offset - offset into the output buffer to begin storing the digest - int len - number of bytes within buf allotted for the digest - int

returns: the number of bytes placed into buf - int

throws: java.security.DigestException - if an error occurs.

get-algorithm clj

(get-algorithm this)

Returns a string that identifies the algorithm, independent of implementation details. The name should be a standard Java Security name (such as "SHA-256"). See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.

returns: the name of the algorithm - java.lang.String

get-digest-length clj

(get-digest-length this)

Returns the length of the digest in bytes, or 0 if this operation is not supported by the provider and the implementation is not cloneable.

returns: the digest length in bytes, or 0 if this operation is not supported by the provider and the implementation is not cloneable. - int

get-provider clj

(get-provider this)

Returns the provider of this message digest object.

returns: the provider of this message digest object - java.security.Provider

reset clj

(reset this)

Resets the digest for further use.

to-string clj

(to-string this)

Returns a string representation of this message digest object.

returns: a string representation of the object. - java.lang.String

update clj

(update this input)

(update this input offset len)

Updates the digest using the specified array of bytes, starting at the specified offset.

input - the array of bytes. - byte[] offset - the offset to start from in the array of bytes. - int len - the number of bytes to use, starting at offset. - int