SHA-256 and SHA3-256 Hashing in Java – Java中的SHA-256和SHA3-256哈希算法

最后修改: 2016年 11月 20日


1. Overview


The SHA (Secure Hash Algorithm) is one of the popular cryptographic hash functions. A cryptographic hash can be used to make a signature for a text or a data file.


In this tutorial, let’s have a look at how we can perform SHA-256 and SHA3-256 hashing operations using various Java libraries.


The SHA-256 algorithm generates an almost unique, fixed-size 256-bit (32-byte) hash. This is a one-way function, so the result cannot be decrypted back to the original value.


Currently, SHA-2 hashing is widely used, as it is considered the most secure hashing algorithm in the cryptographic arena.


SHA-3 is the latest secure hashing standard after SHA-2. Compared to SHA-2, SHA-3 provides a different approach to generate a unique one-way hash, and it can be much faster on some hardware implementations. Similar to SHA-256, SHA3-256 is the 256-bit fixed-length algorithm in SHA-3.


NIST released SHA-3 in 2015, so there are not quite as many SHA-3 libraries as SHA-2 for the time being. It’s not until JDK 9 that SHA-3 algorithms were available in the built-in default providers.

NIST在2015年发布了SHA-3,所以暂时还没有像SHA-2那样多的SHA-3库。直到JDK 9,SHA-3算法才在内置的默认提供者中出现。

Now let’s start with SHA-256.


2. MessageDigest Class in Java


Java provides inbuilt MessageDigest class for SHA-256 hashing:


MessageDigest digest = MessageDigest.getInstance("SHA-256");
byte[] encodedhash = digest.digest(

However, here we have to use a custom byte to hex converter to get the hashed value in hexadecimal:


private static String bytesToHex(byte[] hash) {
    StringBuilder hexString = new StringBuilder(2 * hash.length);
    for (int i = 0; i < hash.length; i++) {
        String hex = Integer.toHexString(0xff & hash[i]);
        if(hex.length() == 1) {
    return hexString.toString();

We need to be aware that the MessageDigest is not thread-safe. Consequently, we should use a new instance for every thread.


3. Guava Library


The Google Guava library also provides a utility class for hashing.

Google Guava库也提供了一个用于散列的实用类。

First, let’s define the dependency:



Next, here’s how we can use Guava to hash a String:


String sha256hex = Hashing.sha256()
  .hashString(originalString, StandardCharsets.UTF_8)

4. Apache Commons Codecs

4.Apache Commons Codecs

Similarly, we can also use Apache Commons Codecs:

同样地,我们也可以使用Apache Commons Codecs。


Here’s the utility class — called DigestUtils — that supports SHA-256 hashing:


String sha256hex = DigestUtils.sha256Hex(originalString);

5. Bouncy Castle Library


5.1. Maven Dependency



5.2. Hashing Using the Bouncy Castle Library

5.2.使用Bouncy Castle库进行哈希运算

The Bouncy Castle API provides a utility class for converting hex data to bytes and back again.

Bouncy Castle API提供了一个实用类,用于将十六进制数据转换为字节,然后再转换回来。

However, we need to populate a digest using the built-in Java API first:

然而,我们需要先用内置的Java API填充一个摘要。

MessageDigest digest = MessageDigest.getInstance("SHA-256");
byte[] hash = digest.digest(
String sha256hex = new String(Hex.encode(hash));

6. SHA3-256


Now let’s continue with SHA3-256. SHA3-256 hashing in Java isn’t that different from SHA-256.


6.1. MessageDigest Class in Java


Starting from JDK 9, we can simply use the built-in SHA3-256 algorithm:

从JDK 9开始,我们可以简单地使用内置的SHA3-256算法。

final MessageDigest digest = MessageDigest.getInstance("SHA3-256");
final byte[] hashbytes = digest.digest(
String sha3Hex = bytesToHex(hashbytes);

6.2. Apache Commons Codecs

6.2.Apache Commons Codecs

Apache Commons Codecs provides a convenient DigestUtils wrapper for the MessageDigest class.

Apache Commons Codecs为MessageDigest类提供了一个方便的DigestUtils包装器。

This library began to support SHA3-256 since version 1.11, and it requires JDK 9+ as well:

这个库从1.11版本开始支持SHA3-256,并且要求JDK 9+也是如此。

String sha3Hex = new DigestUtils("SHA3-256").digestAsHex(originalString);

6.3. Keccak-256


Keccak-256 is another popular SHA3-256 hashing algorithm. Currently, it serves as an alternative to the standard SHA3-256. Keccak-256 delivers the same security level as the standard SHA3-256, and it differs from SHA3-256 only on the padding rule. It has been used in several blockchain projects, such as Monero.


Again, we need to import the Bouncy Castle Library to use Keccak-256 hashing:

同样,我们需要导入Bouncy Castle库来使用Keccak-256散列。

Security.addProvider(new BouncyCastleProvider());
final MessageDigest digest = MessageDigest.getInstance("Keccak-256");
final byte[] encodedhash = digest.digest(
String sha3Hex = bytesToHex(encodedhash);

We can also make use of the Bouncy Castle API to do the hashing:

我们还可以利用Bouncy Castle API来做散列。

Keccak.Digest256 digest256 = new Keccak.Digest256();
byte[] hashbytes = digest256.digest(
String sha3Hex = new String(Hex.encode(hashbytes));

7. Conclusion


In this quick article, we had a look at a few ways of implementing SHA-256 and SHA3-256 hashing in Java, using both built-in and third-party libraries.


The source code of the examples can be found in the GitHub project.