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 world Output: b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9 Input : GeeksForGeeks Output: 112e476505aab51b05aeb2246c02a11df03e1187e886f7c55d4e9935c290ade Input : K1t4fo0V Output: 0a979e43f4874eb24b740c0157994e34636eed0425688161cc58e8b26b1dcf4e
Java
import java.math.BigInteger;import java.nio.charset.StandardCharsets;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;// Java program to calculate SHA hash valueclass GFG2 { 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() < 64) { 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 = "GeeksForGeeks"; System.out.println("\n" + s1 + " : " + toHexString(getSHA(s1))); String s2 = "hello world"; System.out.println("\n" + s2 + " : " + toHexString(getSHA(s2))); String s3 = "K1t4fo0V"; System.out.println("\n" + s3 + " : " + toHexString(getSHA(s3))); } // For specifying wrong message digest algorithms catch (NoSuchAlgorithmException e) { System.out.println("Exception thrown for incorrect algorithm: " + e); } }} |
Output:
HashCode Generated by SHA-256 for: GeeksForGeeks : 112e476505aab51b05aeb2246c02a11df03e1187e886f7c55d4e9935c290ade hello world : b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9 K1t4fo0V : a979e43f4874eb24b740c0157994e34636eed0425688161cc58e8b26b1dcf4e
Application:
- Cryptography
- Data Integrity
