diff --git a/src/Cipher/AdvancedEncryptionStandardCipher.php b/src/Cipher/AdvancedEncryptionStandardCipher.php
index 80db242..0bf45cc 100644
--- a/src/Cipher/AdvancedEncryptionStandardCipher.php
+++ b/src/Cipher/AdvancedEncryptionStandardCipher.php
@@ -7,6 +7,8 @@
 use IlicMiljan\SecureProps\Cipher\Exception\FailedEncryptingValue;
 use IlicMiljan\SecureProps\Cipher\Exception\FailedGeneratingInitializationVector;
 use IlicMiljan\SecureProps\Cipher\Exception\InvalidKeyLength;
+use IlicMiljan\SecureProps\Encoder\Base64Encoder;
+use IlicMiljan\SecureProps\Encoder\Encoder;
 use SensitiveParameter;
 
 class AdvancedEncryptionStandardCipher implements Cipher
@@ -15,11 +17,20 @@ class AdvancedEncryptionStandardCipher implements Cipher
     private const TAG_LENGTH = 16;
     private const KEY_LENGTH = 32;
 
+    private Encoder $encoder;
+
     public function __construct(
         #[SensitiveParameter]
-        private string $key
+        private string $key,
+        ?Encoder $encoder = null
     ) {
         $this->validateKey($key);
+
+        if ($encoder === null) {
+            $this->encoder =  new Base64Encoder();
+        } else {
+            $this->encoder = $encoder;
+        }
     }
 
     /**
@@ -35,15 +46,16 @@ public function encrypt(#[SensitiveParameter] string $string): string
             throw new FailedEncryptingValue();
         }
 
-        return base64_encode($iv . $encryptedString . $tag);
+        return $this->encoder->encode($iv . $encryptedString . $tag);
     }
 
     /**
      * @inheritDoc
+     *
      */
     public function decrypt(#[SensitiveParameter] string $string): string
     {
-        $data = base64_decode($string);
+        $data = $this->encoder->decode($string);
 
         $ivLength = $this->calculateInitializationVectorLength(self::CIPHER);
 
diff --git a/src/Cipher/AsymmetricEncryptionCipher.php b/src/Cipher/AsymmetricEncryptionCipher.php
index ec1e55c..8165f23 100644
--- a/src/Cipher/AsymmetricEncryptionCipher.php
+++ b/src/Cipher/AsymmetricEncryptionCipher.php
@@ -4,14 +4,24 @@
 
 use IlicMiljan\SecureProps\Cipher\Exception\FailedDecryptingValue;
 use IlicMiljan\SecureProps\Cipher\Exception\FailedEncryptingValue;
+use IlicMiljan\SecureProps\Encoder\Base64Encoder;
+use IlicMiljan\SecureProps\Encoder\Encoder;
 use SensitiveParameter;
 
 class AsymmetricEncryptionCipher implements Cipher
 {
+    private Encoder $encoder;
+
     public function __construct(
         private string $publicKey,
-        private string $privateKey
+        private string $privateKey,
+        ?Encoder $encoder = null
     ) {
+        if ($encoder === null) {
+            $this->encoder =  new Base64Encoder();
+        } else {
+            $this->encoder = $encoder;
+        }
     }
 
     /**
@@ -23,7 +33,7 @@ public function encrypt(#[SensitiveParameter] string $string): string
             throw new FailedEncryptingValue();
         }
 
-        return base64_encode($encrypted);
+        return $this->encoder->encode($encrypted);
     }
 
     /**
@@ -31,7 +41,7 @@ public function encrypt(#[SensitiveParameter] string $string): string
      */
     public function decrypt(#[SensitiveParameter] string $string): string
     {
-        $data = base64_decode($string);
+        $data = $this->encoder->decode($string);
 
         if (!openssl_private_decrypt($data, $decrypted, $this->privateKey)) {
             throw new FailedDecryptingValue();
diff --git a/src/Encoder/Base64Encoder.php b/src/Encoder/Base64Encoder.php
new file mode 100644
index 0000000..3d71285
--- /dev/null
+++ b/src/Encoder/Base64Encoder.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace IlicMiljan\SecureProps\Encoder;
+
+use SensitiveParameter;
+
+class Base64Encoder implements Encoder
+{
+    /**
+     * @inheritDoc
+     */
+    public function encode(#[SensitiveParameter] string $value): string
+    {
+        return base64_encode($value);
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function decode(#[SensitiveParameter] string $value): string
+    {
+        return base64_decode($value);
+    }
+}
diff --git a/src/Encoder/Encoder.php b/src/Encoder/Encoder.php
new file mode 100644
index 0000000..a37251d
--- /dev/null
+++ b/src/Encoder/Encoder.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace IlicMiljan\SecureProps\Encoder;
+
+use SensitiveParameter;
+
+/**
+ * Encodes and decodes string values.
+ *
+ * This interface should be implemented by classes that provide mechanisms
+ * for encoding and decoding string values.
+ *
+ * Implementations could, for example, apply base64 encoding/decoding, or any
+ * other form of transformation that maintains the reversibility of the value.
+ */
+interface Encoder
+{
+    /**
+     * Encodes the provided string value.
+     *
+     * Takes a string as input and returns an encoded version of the string.f
+     *
+     * @param string $value The string value to encode.
+     * @return string The encoded string.
+     */
+    public function encode(#[SensitiveParameter] string $value): string;
+
+    /**
+     * Decodes the provided encoded string value.
+     *
+     * Takes an encoded string as input and returns the original unencoded
+     * version of the string.
+     *
+     * @param string $value The encoded string to decode.
+     * @return string The original, unencoded string.
+     */
+    public function decode(#[SensitiveParameter] string $value): string;
+}
diff --git a/src/Encoder/NullEncoder.php b/src/Encoder/NullEncoder.php
new file mode 100644
index 0000000..98fcd22
--- /dev/null
+++ b/src/Encoder/NullEncoder.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace IlicMiljan\SecureProps\Encoder;
+
+use SensitiveParameter;
+
+class NullEncoder implements Encoder
+{
+    /**
+     * @inheritDoc
+     */
+    public function encode(#[SensitiveParameter] string $value): string
+    {
+        return $value;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function decode(#[SensitiveParameter] string $value): string
+    {
+        return $value;
+    }
+}
diff --git a/tests/Attribute/SensitiveParameterTest.php b/tests/Attribute/SensitiveParameterTest.php
new file mode 100644
index 0000000..a97fc34
--- /dev/null
+++ b/tests/Attribute/SensitiveParameterTest.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace IlicMiljan\SecureProps\Tests\Attribute;
+
+use IlicMiljan\SecureProps\Attribute\Encrypted;
+use PHPUnit\Framework\TestCase;
+use SensitiveParameter;
+
+class SensitiveParameterTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        if (PHP_VERSION_ID >= 80200) {
+            $this->markTestSkipped(
+                'All tests in this file have been skipped because they are do not apply to PHP 8.2 or higher.'
+            );
+        }
+    }
+
+    public function testCanBeCreated(): void
+    {
+        $encrypted = new SensitiveParameter();
+
+        $this->assertInstanceOf(SensitiveParameter::class, $encrypted);
+    }
+}
diff --git a/tests/Cipher/AdvancedEncryptionStandardCipherTest.php b/tests/Cipher/AdvancedEncryptionStandardCipherTest.php
index 8e4d09d..863b902 100644
--- a/tests/Cipher/AdvancedEncryptionStandardCipherTest.php
+++ b/tests/Cipher/AdvancedEncryptionStandardCipherTest.php
@@ -3,16 +3,31 @@
 namespace IlicMiljan\SecureProps\Tests\Cipher;
 
 use IlicMiljan\SecureProps\Cipher\AdvancedEncryptionStandardCipher;
+use IlicMiljan\SecureProps\Cipher\Exception\CipherException;
 use IlicMiljan\SecureProps\Cipher\Exception\InvalidKeyLength;
+use IlicMiljan\SecureProps\Encoder\Encoder;
+use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 
 class AdvancedEncryptionStandardCipherTest extends TestCase
 {
+    /** @var Encoder&MockObject */
+    private $encoder;
     private AdvancedEncryptionStandardCipher $cipher;
+    private AdvancedEncryptionStandardCipher $cipherWithCustomEncoder;
 
     protected function setUp(): void
     {
-        $this->cipher = new AdvancedEncryptionStandardCipher(openssl_random_pseudo_bytes(32));
+        $this->encoder = $this->createMock(Encoder::class);
+
+        $this->cipher = new AdvancedEncryptionStandardCipher(
+            openssl_random_pseudo_bytes(32),
+        );
+
+        $this->cipherWithCustomEncoder = new AdvancedEncryptionStandardCipher(
+            openssl_random_pseudo_bytes(32),
+            $this->encoder
+        );
     }
 
     public function testConstructWithInvalidKeyLengthThrowsException(): void
@@ -22,6 +37,9 @@ public function testConstructWithInvalidKeyLengthThrowsException(): void
         new AdvancedEncryptionStandardCipher(openssl_random_pseudo_bytes(16));
     }
 
+    /**
+     * @throws CipherException
+     */
     public function testEncryptAndDecryptSuccessfully(): void
     {
         $encryptedString = $this->cipher->encrypt('plainText');
@@ -29,4 +47,23 @@ public function testEncryptAndDecryptSuccessfully(): void
 
         $this->assertEquals('plainText', $decryptedString);
     }
+
+    /**
+     * @throws CipherException
+     */
+    public function testEncryptAndDecryptWithCustomEncoder(): void
+    {
+        $this->encoder->method('encode')->willReturnCallback(function ($data) {
+            return $data;
+        });
+
+        $this->encoder->method('decode')->willReturnCallback(function ($data) {
+            return $data;
+        });
+
+        $encryptedText = $this->cipherWithCustomEncoder->encrypt('plainText');
+        $decryptedText = $this->cipherWithCustomEncoder->decrypt($encryptedText);
+
+        $this->assertEquals('plainText', $decryptedText);
+    }
 }
diff --git a/tests/Cipher/AsymmetricEncryptionCipherTest.php b/tests/Cipher/AsymmetricEncryptionCipherTest.php
index 356ad23..52f191b 100644
--- a/tests/Cipher/AsymmetricEncryptionCipherTest.php
+++ b/tests/Cipher/AsymmetricEncryptionCipherTest.php
@@ -3,15 +3,23 @@
 namespace IlicMiljan\SecureProps\Tests\Cipher;
 
 use IlicMiljan\SecureProps\Cipher\AsymmetricEncryptionCipher;
+use IlicMiljan\SecureProps\Cipher\Exception\CipherException;
+use IlicMiljan\SecureProps\Encoder\Encoder;
 use OpenSSLAsymmetricKey;
+use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 
 class AsymmetricEncryptionCipherTest extends TestCase
 {
+    /** @var Encoder&MockObject */
+    private $encoder;
     private AsymmetricEncryptionCipher $cipher;
+    private AsymmetricEncryptionCipher $cipherWithCustomEncoder;
 
     protected function setUp(): void
     {
+        $this->encoder = $this->createMock(Encoder::class);
+
         /** @var OpenSSLAsymmetricKey $asymmetricKey */
         $asymmetricKey = openssl_pkey_new();
         /** @var string[] $asymmetricKeyDetails */
@@ -20,8 +28,17 @@ protected function setUp(): void
         openssl_pkey_export($asymmetricKey, $privateKey);
 
         $this->cipher = new AsymmetricEncryptionCipher($asymmetricKeyDetails['key'], $privateKey);
+
+        $this->cipherWithCustomEncoder = new AsymmetricEncryptionCipher(
+            $asymmetricKeyDetails['key'],
+            $privateKey,
+            $this->encoder
+        );
     }
 
+    /**
+     * @throws CipherException
+     */
     public function testEncryptAndDecryptSuccessfully(): void
     {
         $encryptedString = $this->cipher->encrypt('plainText');
@@ -29,4 +46,23 @@ public function testEncryptAndDecryptSuccessfully(): void
 
         $this->assertEquals('plainText', $decryptedString);
     }
+
+    /**
+     * @throws CipherException
+     */
+    public function testEncryptAndDecryptWithCustomEncoder(): void
+    {
+        $this->encoder->method('encode')->willReturnCallback(function ($data) {
+            return $data;
+        });
+
+        $this->encoder->method('decode')->willReturnCallback(function ($data) {
+            return $data;
+        });
+
+        $encryptedText = $this->cipherWithCustomEncoder->encrypt('plainText');
+        $decryptedText = $this->cipherWithCustomEncoder->decrypt($encryptedText);
+
+        $this->assertEquals('plainText', $decryptedText);
+    }
 }
diff --git a/tests/Encoder/Base64EncoderTest.php b/tests/Encoder/Base64EncoderTest.php
new file mode 100644
index 0000000..0a3c5f9
--- /dev/null
+++ b/tests/Encoder/Base64EncoderTest.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace IlicMiljan\SecureProps\Tests\Encoder;
+
+use IlicMiljan\SecureProps\Encoder\Base64Encoder;
+use PHPUnit\Framework\TestCase;
+
+class Base64EncoderTest extends TestCase
+{
+    private Base64Encoder $encoder;
+
+    protected function setUp(): void
+    {
+        $this->encoder = new Base64Encoder();
+    }
+
+    public function testEncode(): void
+    {
+        $string = "Hello, World!";
+        $expectedEncodedString = base64_encode($string);
+
+        $this->assertEquals(
+            $expectedEncodedString,
+            $this->encoder->encode($string),
+            "The encoded string does not match the expected output."
+        );
+    }
+
+    public function testDecode(): void
+    {
+        $encodedString = "SGVsbG8sIFdvcmxkIQ==";
+        $expectedDecodedString = base64_decode($encodedString);
+
+        $this->assertEquals(
+            $expectedDecodedString,
+            $this->encoder->decode($encodedString)
+        );
+    }
+
+    public function testEncodeDecode(): void
+    {
+        $originalString = "Test encode and decode!";
+
+        $encodedString = $this->encoder->encode($originalString);
+        $decodedString = $this->encoder->decode($encodedString);
+
+        $this->assertEquals(
+            $originalString,
+            $decodedString
+        );
+    }
+}
diff --git a/tests/Encoder/NullEncoderTest.php b/tests/Encoder/NullEncoderTest.php
new file mode 100644
index 0000000..a02bf52
--- /dev/null
+++ b/tests/Encoder/NullEncoderTest.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace IlicMiljan\SecureProps\Tests\Encoder;
+
+use IlicMiljan\SecureProps\Encoder\NullEncoder;
+use PHPUnit\Framework\TestCase;
+
+class NullEncoderTest extends TestCase
+{
+    private NullEncoder $encoder;
+
+    protected function setUp(): void
+    {
+        $this->encoder = new NullEncoder();
+    }
+
+    public function testEncode(): void
+    {
+        $string = "This is a test string.";
+
+        $this->assertEquals(
+            $string,
+            $this->encoder->encode($string)
+        );
+    }
+
+    public function testDecode(): void
+    {
+        $string = "Decoding test string.";
+
+        $this->assertEquals(
+            $string,
+            $this->encoder->decode($string)
+        );
+    }
+
+    public function testEncodeDecode(): void
+    {
+        $originalString = "Encode then decode this!";
+
+        $encodedString = $this->encoder->encode($originalString);
+        $decodedString = $this->encoder->decode($encodedString);
+
+        /** @noinspection PhpConditionAlreadyCheckedInspection */
+        $this->assertEquals(
+            $originalString,
+            $decodedString,
+        );
+    }
+}
diff --git a/tests/Exception/SingleEncryptedAttributeExpectedTest.php b/tests/Exception/SingleEncryptedAttributeExpectedTest.php
new file mode 100644
index 0000000..6970932
--- /dev/null
+++ b/tests/Exception/SingleEncryptedAttributeExpectedTest.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace IlicMiljan\SecureProps\Tests\Exception;
+
+use IlicMiljan\SecureProps\Exception\EncryptionServiceException;
+use IlicMiljan\SecureProps\Exception\SingleEncryptedAttributeExpected;
+use IlicMiljan\SecureProps\Exception\ValueMustBeObject;
+use PHPUnit\Framework\TestCase;
+use RuntimeException;
+
+class SingleEncryptedAttributeExpectedTest extends TestCase
+{
+    private int $count;
+
+    protected function setUp(): void
+    {
+        $this->count = 1;
+    }
+
+    public function testCanBeCreated(): void
+    {
+        $exception = new SingleEncryptedAttributeExpected($this->count);
+
+        $this->assertInstanceOf(SingleEncryptedAttributeExpected::class, $exception);
+    }
+
+    public function testReturnsCount(): void
+    {
+        $exception = new SingleEncryptedAttributeExpected($this->count);
+
+        $this->assertEquals($this->count, $exception->getCount());
+    }
+
+    public function testPreviousExceptionIsStored(): void
+    {
+        $previous = new RuntimeException('Previous exception');
+        $exception = new SingleEncryptedAttributeExpected($this->count, $previous);
+
+        $this->assertSame($previous, $exception->getPrevious());
+    }
+
+    public function testImplementsEncryptionServiceExceptionInterface(): void
+    {
+        $exception = new SingleEncryptedAttributeExpected($this->count);
+
+        $this->assertInstanceOf(EncryptionServiceException::class, $exception);
+    }
+}