How Do I Avoid Conversion Issues When Encrypting Data Between Byte Arrays and Strings?

Addressing Conversion Issues Between Byte Arrays and Strings in Encryption

In the context of encryption, converting byte arrays to strings and back can pose challenges, often resulting in mismatched values and decryption errors. Here's an exploration of these issues and a detailed solution.

Consider the following encryption scenario:

public class NewEncrypter {

    // Encryption and decryption are performed on byte arrays, not strings
    public byte[] encrypt(String input) throws Exception {
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return cipher.doFinal(input.getBytes("UTF-16"));
    }

    public String decrypt(byte[] encryptionBytes) throws Exception {
        cipher.init(Cipher.DECRYPT_MODE, key);
        return new String(cipher.doFinal(encryptionBytes), "UTF-16");
    }
}

However, storing encrypted data as strings is discouraged due to their intended use for human-readable text, not arbitrary binary data. If it's unavoidable, using an encoding with a 1-to-1 mapping between bytes and characters is crucial.

ISO-8859-1 Encoding

For this specific scenario, the ISO-8859-1 encoding is recommended:

    String decoded = new String(encryptedByteArray, "ISO-8859-1");
    byte[] encoded = decoded.getBytes("ISO-8859-1");

Avoiding Common Encoding Pitfalls

UTF-16 encoding can cause issues because:

• String.getBytes("UTF-16") adds a byte order marker character.
• Not all byte sequences can be mapped to UTF-16 characters (e.g., 4-byte sequences with invalid character mappings).

Alternative Encodings

If ISO-8859-1 does not meet your requirements, consider using hexadecimal or base64 encoding. However, these require additional helper libraries since they are not defined in the standard API.

By adhering to these guidelines and using an appropriate encoding, you can resolve the discrepancies between byte arrays and strings in your encryption process.

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