diff --git a/client/src/der.vala b/client/src/der.vala
index d572147..bfdcfd9 100644
--- a/client/src/der.vala
+++ b/client/src/der.vala
@@ -7,24 +7,26 @@ namespace StudySystemClient.Der {
 
 	private const uint BASE_HEADER_SIZE = 2;
 
-	public static Datum decode(uint8[] bytes) throws DecodeError {
+	public static Datum decode(uint8[] bytes, out uint? size = null)
+			throws DecodeError {
 		if (bytes.length < BASE_HEADER_SIZE) {
 			throw new DecodeError.INCOMPLETE(
 				"Message is fewer than %u bytes", BASE_HEADER_SIZE);
 		}
 
-		uint header_size = 0;
-		var length = decode_length(bytes, ref header_size);
+		uint header_size;
+		var length = decode_length(bytes, out header_size);
 		if (header_size + length > bytes.length) {
 			throw new DecodeError.INCOMPLETE(
 				"Length %u but only %u bytes available", length,
 				bytes.length - header_size);
 		}
 		var content = bytes[header_size:header_size + length];
+		size = header_size + length;
 		return decode_datum(bytes[0], content);
 	}
 
-	private static uint decode_length(uint8[] bytes, ref uint header_size)
+	private static uint decode_length(uint8[] bytes, out uint header_size)
 			throws DecodeError {
 		if ((bytes[1] & 0x80) != 0) {
 			var length_size = bytes[1] & 0x7f;
@@ -53,6 +55,8 @@ namespace StudySystemClient.Der {
 			return new Integer.from_content(content);
 		case Utf8String.TYPE:
 			return new Utf8String.from_content(content);
+		case Sequence.TYPE:
+			return new Sequence.from_content(content);
 		default:
 			throw new DecodeError.UNKNOWN_TYPE("Unsupported type: %02x",
 											   type);
@@ -214,11 +218,48 @@ namespace StudySystemClient.Der {
 			value = decode_string(bytes);
 		}
 
-		public static string decode_string(uint8[] bytes) {
+		private static string decode_string(uint8[] bytes) {
 			var buffer = new uint8[bytes.length + 1];
 			Memory.copy(buffer, bytes, bytes.length);
 			buffer[bytes.length] = 0;
 			return (string)buffer;
 		}
 	}
+
+	public class Sequence : Datum {
+		internal const uint8 TYPE = 0x30;
+
+		public Datum[] value { get; private set; }
+
+		public Sequence(Datum[] val) {
+			type = TYPE;
+			content = encode_array(val);
+			value = val;
+		}
+
+		internal Sequence.from_content(uint8[] bytes) throws DecodeError {
+			type = TYPE;
+			content = bytes;
+			value = decode_array(bytes);
+		}
+
+		private static uint8[] encode_array(Datum[] val) {
+			var buffer = new ByteArray();
+			foreach (var datum in val)
+				buffer.append(datum.encode());
+			return buffer.data;
+		}
+
+		private static Datum[] decode_array(uint8[] bytes)
+								   throws DecodeError {
+			var elems = new GenericArray<Datum>();
+			uint offset = 0;	
+			uint size;
+			while (offset < bytes.length) {
+				elems.add(decode(bytes[offset:], out size));
+				offset += size;
+			}
+			return elems.data;
+		}
+	}
 }
diff --git a/client/tests/der_tests.vala b/client/tests/der_tests.vala
index cf3d3ce..ec9433a 100644
--- a/client/tests/der_tests.vala
+++ b/client/tests/der_tests.vala
@@ -1,3 +1,4 @@
+using StudySystemClient;
 using StudySystemClient.Der;
 
 static bool bytes_equal(uint8[] expected, uint8[] actual) {
@@ -46,15 +47,31 @@ static void test_decode_boolean(uint8[] bytes, bool expected) {
 }
 
 static void test_decode_integer(uint8[] bytes, int64 expected) {
-	Integer integer;
+	Datum datum;
 	try {
-		integer = decode(bytes) as Integer;
+		datum = decode(bytes);
+	} catch (DecodeError err) {
+		Test.message("Decoding failed: %s", err.message);
+		Test.fail();
+		return;
+	}	
+	test_integer_value(expected, datum);
+}
+
+static void test_decode_utf8string(uint8[] bytes, string expected) {
+	Datum datum;
+	try {
+		datum = decode(bytes);
 	} catch (DecodeError err) {
 		Test.message("Decoding failed: %s", err.message);
 		Test.fail();
 		return;
 	}
+	test_utf8string_value(expected, datum);
+}
 
+static void test_integer_value(int64 expected, Datum datum) {
+	var integer = datum as Integer;
 	if (integer == null) {
 		Test.message("Bytes were not decoded as a INTEGER");
 		Test.fail();
@@ -67,16 +84,8 @@ static void test_decode_integer(uint8[] bytes, int64 expected) {
 	}
 }
 
-static void test_decode_utf8string(uint8[] bytes, string expected) {
-	Utf8String utf8string;
-	try {
-		utf8string = decode(bytes) as Utf8String;
-	} catch (DecodeError err) {
-		Test.message("Decoding failed: %s", err.message);
-		Test.fail();
-		return;
-	}
-
+static void test_utf8string_value(string expected, Datum datum) {
+	var utf8string = datum as Utf8String;
 	if (utf8string == null) {
 		Test.message("Bytes were not decoded as a UTF8String");
 		Test.fail();
@@ -154,6 +163,15 @@ void main(string[] args) {
 			test_encode(new Utf8String(string.nfill(128, 'x')), expected);
 		});
 
+	Test.add_func("/encode/sequence/foo,42", () => {
+			var sequence = new Der.Sequence(
+				{new Utf8String("foo"), new Integer(42)});
+			var expected = new uint8[] {
+				0x30, 0x08, 0x0c, 0x03, 0x66, 0x6f, 0x6f, 0x02, 0x01, 0x2a
+			};
+			test_encode(sequence, expected);
+		});
+
 	/*
 	 * Decoding
 	 */
@@ -208,5 +226,34 @@ void main(string[] args) {
 			test_decode_utf8string(bytes, string.nfill(128, 'x'));
 		});
 
+	Test.add_func("/decode/sequence/foo,42", () => {
+			var bytes = new uint8[] {
+				0x30, 0x08, 0x0c, 0x03, 0x66, 0x6f, 0x6f, 0x02, 0x01, 0x2a
+			};
+			var expected = 2;
+			Der.Sequence sequence;
+			try {
+				sequence = decode(bytes) as Der.Sequence;
+			} catch (DecodeError err) {
+				Test.message("Decoding failed: %s", err.message);
+				Test.fail();
+				return;
+			}
+			if (sequence == null) {
+				Test.message("Bytes were not decoded as a SEQUENCE");
+				Test.fail();
+				return;
+			}
+			Datum[] elems = sequence.value;
+			if (elems.length != expected) {
+				Test.message(
+					@"Expected $expected elements, got $(elems.length)");
+				Test.fail();
+				return;
+			}
+			test_utf8string_value("foo", elems[0]);
+			test_integer_value(42, elems[1]);
+		});
+
 	Test.run();
 }