MessageDigest in Java
MessageDigest is the returned value of the hash function, which is also known as has values. Hash functions are mostly used in each and every information security application. Hash functions are used for converting numerical values into compressed numerical values. For Hash functions, the length of the user-given input can be arbitrary, but the length of the output is always of fixed length.
The java.security package provides a class, i.e., MessageDigest, that supports algorithms such as SHA-1, SHA 256, and MD5 etc., for converting a message of arbitrary length to a message digest.
In order to convert a message into MessageDigest, we use the following steps:
1. In the first step, we will create an instance of the MessageDigest by using the getInstance() method of the MessageDigest The getInstance() method accepts a parameter, i.e., algo, which defines the algorithm to be used.
The getInstance() method returns a MessageDigest object implementing the specified algorithm.
2. In the next step, we will pass the message to the created MessageDigest instance. For passing the value, we use the update() method of the MessageDigest class. The update() method accepts data in the form of the byte array.
3. In the next step, we will use the digest() method of the MessageDigest class to generate the message digest. The digest() method is responsible for computing the hash function on the current object. The digest() method returns the message digest in the form of the byte array.
Let's implement the code for understanding how we can use the MessageDigest class by using the above steps:
The getInstance() method of the MessageDigest class can throw the NoSuchAlgorithmException when no provider supports the message digest spi application for the particular algorithm.