diff --git a/crypto/src/main/kotlin/org/openrs2/crypto/Sha1.kt b/crypto/src/main/kotlin/org/openrs2/crypto/Sha1.kt
new file mode 100644
index 00000000..1c6b6e0a
--- /dev/null
+++ b/crypto/src/main/kotlin/org/openrs2/crypto/Sha1.kt
@@ -0,0 +1,19 @@
+package org.openrs2.crypto
+
+import io.netty.buffer.ByteBuf
+import io.netty.buffer.ByteBufUtil
+import java.security.MessageDigest
+
+public fun ByteBuf.sha1(): ByteArray {
+    return sha1(readerIndex(), readableBytes())
+}
+
+public fun ByteBuf.sha1(index: Int, len: Int): ByteArray {
+    val digest = MessageDigest.getInstance("SHA-1")
+    if (hasArray()) {
+        digest.update(array(), arrayOffset() + index, len)
+    } else {
+        digest.update(ByteBufUtil.getBytes(this, index, len, false))
+    }
+    return digest.digest()
+}