diff --git a/aes/src/commonMain/kotlin/com/mooncloak/kodetools/aes/BlockCipherMode.kt b/aes/src/commonMain/kotlin/com/mooncloak/kodetools/aes/BlockCipherMode.kt
new file mode 100644
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--- /dev/null
+++ b/aes/src/commonMain/kotlin/com/mooncloak/kodetools/aes/BlockCipherMode.kt
@@ -0,0 +1,26 @@
+package com.mooncloak.kodetools.aes
+
+import kotlinx.serialization.Serializable
+import kotlin.jvm.JvmInline
+
+/**
+ * Defines how large sets of data are combined during AES encryption. AES encrypts 16 byte blocks of data, but for data
+ * larger than 16 bytes, they have to be combined. The approach to how large data is combined (for example,
+ * concatenated, or XORed with the previous cipher text, etc.) is defined by separate specifications and identified by
+ * instances of this class. Note that only some common modes are supported by this AES implementation.
+ */
+@JvmInline
+@Serializable
+public value class BlockCipherMode public constructor(
+    public val value: String
+) {
+
+    public companion object {
+
+        public val ECB: BlockCipherMode = BlockCipherMode(value = "ECB")
+
+        public val CBC: BlockCipherMode = BlockCipherMode(value = "CBC")
+
+        public val GCM: BlockCipherMode = BlockCipherMode(value = "GCM")
+    }
+}