How to Implement Secure String Hashing in Java with SHA-256?

Java Hash String using SHA-256

Hashing a string using SHA-256 in Java may seem like a straightforward task, but there are crucial differences between hashing and encoding that require clarification.

SHA-256 (Secure Hash Algorithm-256) is not an encoding mechanism; it's a one-way hash function. This means that when you hash a string, you produce an irreversible sequence of binary data.

To apply SHA-256 hashing in Java, follow these steps:

1. Convert String to Bytes: Convert the input string into a byte array using a character encoding like UTF-8.

<code class="java">byte[] bytes = text.getBytes(StandardCharsets.UTF_8);</code>

2. Create MessageDigest Instance: Instantiate the SHA-256 message digest algorithm.

<code class="java">MessageDigest digest = MessageDigest.getInstance("SHA-256");</code>

3. Update Message Digest: Feed the byte array representing the string into the message digest.

<code class="java">digest.update(bytes);</code>

4. Calculate Hash: Generate the hash value from the message digest.

<code class="java">byte[] hash = digest.digest();</code>

Important Note:

The resulting hash is in binary format. If you wish to represent it as a string, consider using base64 or hexadecimal encoding. Avoid using the String(byte[], String) constructor, as it may result in garbled characters.

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