Definition:
In Cryptography, SHA is cryptographic hash function which takes input as 20 Bytes and rendered the hash value in hexadecimal number, 40 digits long approx.
Message Digest Class:
To calculate cryptographic hashing value in Java, MessageDigest Class is used, under the package java.security.
MessagDigest Class provides following cryptographic hash function to find hash value of a text, they are:
MD5
SHA-1
SHA-256
This Algorithms are initialized in static method called getInstance(). After selecting the algorithm it calculate the digest value and return the results in byte array.
BigInteger class is used, which converts the resultant byte array into its sign-magnitude representation. This representation is converted into hex format to get the MessageDigest
Examples:
Input : Hello Everyone
Output : b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9
Input : Prutor.ai
Output : 112e476505aab51b05aeb2246c02a11df03e1187e886f7c55d4e9935c290ade
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
// Java program to calculate SHA hash value
class Prutor {
public static byte[] getSHA(String input) throws NoSuchAlgorithmException
{
// Static getInstance method is called with hashing SHA
MessageDigest md = MessageDigest.getInstance("SHA-256");
// digest() method called
// to calculate message digest of an input
// and return array of byte
return md.digest(input.getBytes(StandardCharsets.UTF_8));
}
public static String toHexString(byte[] hash)
{
// Convert byte array into signum representation
BigInteger number = new BigInteger(1, hash);
// Convert message digest into hex value
StringBuilder hexString = new StringBuilder(number.toString(16));
// Pad with leading zeros
while (hexString.length() < 32)
{
hexString.insert(0, '0');
}
return hexString.toString();
}
// Driver code
public static void main(String args[])
{
try
{
System.out.println("HashCode Generated by SHA-256 for:");
String s1 = "Prutor.ai";
System.out.println("n" + s1 + " : " + toHexString(getSHA(s1)));
String s2 = "Hello Everyone";
System.out.println("n" + s2 + " : " + toHexString(getSHA(s2)));
}
// For specifying wrong message digest algorithms
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown for incorrect algorithm: " + e);
}
}
}
Result :
HashCode Generated by SHA-256 for:
Prutor.ai : 112e476505aab51b05aeb2246c02a11df03e1187e886f7c55d4e9935c290ade
Hello Everyone : b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9
Application:
Cryptography
Data Integrity