Situatie
The SHA-2 family of cryptographic hash functions consists of six hash functions. These are:
- SHA-224, with 224 bit hash values
- SHA-256, with 256 bit hash values
- SHA-384, with 384 bit hash values
- SHA-512, with 512 bit hash values
- SHA-512/224, with 512 bit hash values
- SHA-512/256, with 512 bit hash valuesAmong these, SHA-256 and SHA-512 are the most commonly accepted and used hash functions computed with 32-bit and 64-bit words, respectively. SHA-224 and SHA-384 are truncated versions of SHA-256 and SHA-512 respectively, computed with different initial values.
Solutie
Pasi de urmat
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 as follows:
- MD2
- MD5
- SHA-1
- SHA-224
- SHA-256
- SHA-384
- SHA-512
These algorithms are initialized in static method called getInstance(). After selecting the algorithm the message digest value is calculated and the results is returned as byte array. BigInteger class is used, to convert the resultant byte array into its signum representation. This representation is then converted into hexadecimal format to get the expected MessageDigest.
Below program shows the implementation of SHA-512 hash function:
// Java program to calculate SHA-512 hash value
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class GFG {
public static String encryptThisString(String input)
{
try {
// getInstance() method is called with algorithm SHA-512
MessageDigest md = MessageDigest.getInstance(“SHA-512”);
// digest() method is called
// to calculate message digest of the input string
// returned as array of byte
byte[] messageDigest = md.digest(input.getBytes());
// Convert byte array into signum representation
BigInteger no = new BigInteger(1, messageDigest);
// Convert message digest into hex value
String hashtext = no.toString(16);
// Add preceding 0s to make it 32 bit
while (hashtext.length() < 32) {
hashtext = “0” + hashtext;
}
// return the HashText
return hashtext;
}
// For specifying wrong message digest algorithms
catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
}
// Driver code
public static void main(String args[]) throws NoSuchAlgorithmException
{
System.out.println(“HashCode Generated by SHA-512 for: “);
String s1 = “GeeksForGeeks”;
System.out.println(“\n” + s1 + ” : ” + encryptThisString(s1));
String s2 = “hello world”;
System.out.println(“\n” + s2 + ” : ” + encryptThisString(s2));
}
}
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