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| </div><div id='content' class='page-1'><div class='row'><div class='row-fluid'><div class='col-lg-3'><ul class='nav-sidebar'><li><a href='./'>Blog index</a></li><li class='active'><a href='#doc'>Encryption and decryption with Groovy</a></li><li><a href='#_using_the_jdk_crypto_classes' class='anchor-link'>Using the JDK crypto classes</a></li><li><a href='#_using_the_bouncy_castle_library' class='anchor-link'>Using the Bouncy Castle library</a></li><li><a href='#_other_useful_functionality' class='anchor-link'>Other useful functionality</a></li><li><a href='#_references' class='anchor-link'>References</a></li><li><a href='#_conclusion' class='anchor-link'>Conclusion</a></li></ul></div><div class='col-lg-8 col-lg-pull-0'><a name='doc'></a><h1>Encryption and decryption with Groovy</h1><p><span>Author: <i>Paul King</i></span><br/><span>Published: 2022-09-19 02:34PM</span></p><hr/><div id="preamble"> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Inspired by this recent <a href="https://asyncq.com/how-to-encrypt-and-decrypt-data-in-java">blog entry</a>, here is an example showing how to encrypt and decrypt with Groovy.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_using_the_jdk_crypto_classes">Using the JDK crypto classes</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>First, we need some text to encrypt. We’ll use an excerpt of the one from the aforementioned blog post:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">var text = 'Contrary to popular belief, Lorem Ipsum is not simply random text. It has \ |
| roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old.'</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Next, we’ll create a factory for our cipher instance, generate a key, and set up an initialization vector.</p> |
| </div> |
| <div class="paragraph"> |
| <p>First, the cipher factory:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">var factory = { Cipher.getInstance('AES/CBC/PKCS5Padding') }</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>For our cipher algorithm, we are using the Advanced Encryption Standard (<a href="https://en.wikipedia.org/wiki/Advanced_Encryption_Standard">AES</a>) algorithm, in Cipher Block Chaining (<a href="https://www.highgo.ca/2019/08/08/the-difference-in-five-modes-in-the-aes-encryption-algorithm/">CBC</a>) mode, with <a href="https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS#5_and_PKCS#7">PKCS5 padding</a>. We’ll look at other options later.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Next we generate our secret key. Our secret key is our password. Only someone who has the password will be able to decrypt the encrypted message. We could use any random bits for our key, but like passwords, we want to choose a strong key rather than a weak one. Cryptographic libraries provide classes to generate such keys. We just need to provide the key size. AES supports 128, 192 and 256-bit keys. We’ll choose 192 here:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">var key = generateKey('AES', 192)</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Our code uses this helper method:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">def generateKey(String algorithm, Integer size) { |
| var generator = KeyGenerator.getInstance(algorithm) |
| generator.init(size) |
| generator.generateKey() |
| }</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Next, we generate an initialization vector:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">var ivParameterSpec = randomParameterSpec(factory)</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>It uses this helper method (we’re using the algorithm block size for our initialization vector size):</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">def randomParameterSpec(Closure<Cipher> factory) { |
| var block = new byte[factory().blockSize] |
| SecureRandom.instanceStrong.nextBytes(block) |
| new IvParameterSpec(block) |
| }</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>An <a href="https://en.wikipedia.org/wiki/Initialization_vector">initialization vector</a> is used to introduce some additional randomness to avoid repeating patterns in the input leading to repeating patterns in the encrypted bytes.</p> |
| </div> |
| <div class="paragraph"> |
| <p>With all these things in place, we are almost ready to encrypt or decrypt, but first, let’s define two more helper methods:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">def encrypt(byte[] bytes, Key key, IvParameterSpec spec, Closure<Cipher> factory) { |
| var cipher = factory() |
| cipher.init(ENCRYPT_MODE, key, spec) |
| cipher.doFinal(bytes) |
| } |
| |
| def decrypt(byte[] bytes, Key key, IvParameterSpec spec, Closure<Cipher> factory) { |
| var cipher = factory() |
| cipher.init(DECRYPT_MODE, key, spec) |
| cipher.doFinal(bytes) |
| }</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>And here is how we encrypt and decrypt:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">var encrypted = encrypt(text.bytes, key, ivParameterSpec, factory) |
| println "Encrypted bytes : $encrypted" |
| println "Encrypted text : ${new String(encrypted)}" |
| |
| var decrypted = decrypt(encrypted, key, ivParameterSpec, factory) |
| println "Decrypted bytes : $decrypted" |
| println "Decrypted text : ${new String(decrypted)}"</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Which has this output:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code>Encrypted bytes : [-117, 36, 18, 69, -101, -8, 35, 93, -102, -49, -12, …, -19, -100] |
| Encrypted text : ‹$E›ø#]šÏôæ”Á˜çp^µ³=L(Ö^_ŒC>CIË„ö,1É8ÆŸ.Š?vßG,Èw‰å¼zÜf>?µ›D¹éÆk€ °˜2êÔ}í©àhl$>?¹¡Kå3ÔO?±&…êî¶Ê–¾°®q®à—0ú‘ÔhO<H¦ç®Ç”ÈhAëjó QPyƒy6Ĥ*´un¼ï¯m¨´ÙjeJtëº\ó6 ƪKªœíœ |
| Decrypted bytes : [67, 111, 110, 116, 114, 97, 114, 121, 32, 116, 111, 32, …, 100, 46] |
| Decrypted text : Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old.</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>We can see that everything worked as expected, since the final output matches our original input text.</p> |
| </div> |
| <div class="paragraph"> |
| <p>We can alternatively, swap algorithms. There are numerous <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/javax/crypto/Cipher.html">algorithms and modes supported</a> by the JDK and others supported by third-party libraries. A nice summary can be found <a href="https://en.wikipedia.org/wiki/Comparison_of_cryptography_libraries">here</a>. Let’s have a look at using a different algorithm.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_using_the_bouncy_castle_library">Using the Bouncy Castle library</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>We’ll swap to use the CAST5 (<a href="https://en.wikipedia.org/wiki/CAST-128">CAST-128</a>) algorithm |
| which supports up to a 128-bit key. We’ll use <a href="https://en.wikipedia.org/w/index.php?title=HMAC-SHA1">HMAC-SHA1</a> to generate our key.</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">import org.bouncycastle.jce.provider.BouncyCastleProvider |
| var bc = new BouncyCastleProvider() |
| factory = { Cipher.getInstance('CAST5', bc) } |
| key = generateKey('HmacSHA1', 128) |
| ivParameterSpec = randomParameterSpec(factory)</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>CAST5 is the default algorithm used in some versions of GPG and PGP. |
| It isn’t included by default in the JDK, so for this we’ll use the |
| <a href="https://www.bouncycastle.org/java.html">Bouncy Castle library</a>.<br></p> |
| </div> |
| <div class="paragraph"> |
| <p><em>NOTE</em></p> |
| </div> |
| <div class="sidebarblock"> |
| <div class="content"> |
| <div class="paragraph"> |
| <p>Just as an aside, if you are wanting to encrypt or decrypt GPG/PGP files, don’t use the above code. Libraries like Bouncy Castle have <a href="https://www.bouncycastle.org/docs/pgdocs1.8on/index.html">dedicated classes</a> for such scenarios.</p> |
| </div> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>We now encrypt and decrypt as before:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">encrypted = encrypt(text.bytes, key, ivParameterSpec, factory) |
| println "Encrypted text : ${new String(encrypted)}" |
| decrypted = decrypt(encrypted, key, ivParameterSpec, factory) |
| println "Decrypted text : ${new String(decrypted)}"</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Which has this output:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code>Encrypted text : Mªá?r?v9£÷~4µT'›ÙÝÁl¿Þg¾0ñŽ¡?Ü=³9 Q¬»3«ÖÁ¡µ ¾@4÷`FñÙŠfø7¥#›v¤Í–‰¼Ü¢ƒE6ô ŽTÙlæÏz>o?àL›¡¢z1nÖo9]šOÔ¼SÔOÍ#Ý7LœÀî}ó5m%q•»l% /AWT´¢zH#t솱l¶£—Œ «©wˆÃ®>®Ü6ër-E |
| Decrypted text : Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old.</code></pre> |
| </div> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_other_useful_functionality">Other useful functionality</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>Passing around binary data like our secret key or the encrypted data, has its own problems. Groovy provides extension methods to <code>encode</code> such data (and corresponding <code>decode</code> methods). For example, we can encode our secret key in various ways:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">var keyBytes = key.encoded |
| println keyBytes.encodeHex() |
| println keyBytes.encodeBase64() |
| println keyBytes.encodeBase64Url()</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Which has this output (the key is random, so the output will differ for each run):</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code>85a0d3f0ce0cbe6402dc9579fbffcf1d |
| haDT8M4MvmQC3JV5+//PHQ== |
| haDT8M4MvmQC3JV5-__PHQ</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Groovy also provides extension methods for various checksums (but you might want to look at stronger checksum algorithms in security sensitive scenarios):</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="groovy">println "SHA256 : ${text.sha256()}" |
| println "MD5 : ${text.md5()}"</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Which has this output:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code>SHA256 : ccb184e35e4c32bafc730d84ec924ea2980035ea5fadb012e3b2b31abf4323c9 |
| MD5 : 46c61a174c2dc99204521ca89f09f63c</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>If you are encrypting and decrypting entire files, the JDK has special classes for that too which are also easy to use from Groovy. That’s all for now.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_references">References</h2> |
| <div class="sectionbody"> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p><a href="https://en.wikipedia.org/wiki/Comparison_of_cryptography_libraries">Comparison of cryptography libraries</a> (Wikipedia)</p> |
| </li> |
| <li> |
| <p><a href="https://asyncq.com/how-to-encrypt-and-decrypt-data-in-java">How to encrypt and decrypt data in Java</a> (also on <a href="https://i-sammy.medium.com/how-to-encrypt-and-decrypt-data-in-java-de41be237422">medium.com</a>)</p> |
| </li> |
| <li> |
| <p><a href="https://mvnrepository.com/artifact/org.bouncycastle/bcprov-jdk18on/1.71.1">Bouncy castle</a> in maven central</p> |
| </li> |
| <li> |
| <p><a href="https://www.baeldung.com/java-aes-encryption-decryption">AES Encryption and Decryption in Java</a> (Baeldung)</p> |
| </li> |
| <li> |
| <p><a href="https://www.baeldung.com/java-encryption-iv">Initialization Vector for Encryption in Java</a> (Baeldung)</p> |
| </li> |
| <li> |
| <p><a href="https://www.baeldung.com/java-3des">3DES in Java</a> (Baeldung)</p> |
| </li> |
| </ul> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="_conclusion">Conclusion</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>We have taken a brief look at encrypting and decrypting with Apache Groovy.</p> |
| </div> |
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