add beginning of IDEA vector source docs. no verification code yet
diff --git a/docs/development/custom-vectors/idea.rst b/docs/development/custom-vectors/idea.rst
new file mode 100644
index 0000000..097819e
--- /dev/null
+++ b/docs/development/custom-vectors/idea.rst
@@ -0,0 +1,25 @@
+IDEA Vector Creation
+=====================
+
+This page documents the code that was used to generate the IDEA CBC, CFB, and
+OFB test vectors as well as the code used to verify them against another
+implementation. For IDEA the vectors were generated using OpenSSL and verified
+with Go.
+
+Creation
+--------
+
+``cryptography`` was modified to support IDEA in CBC, CFB, and OFB modes. Then
+the following python script was run to generate the vector files.
+
+.. literalinclude:: /development/custom-vectors/idea/generate_idea.py
+
+Download link: :download:`generate_idea.py </development/custom-vectors/idea/generate_idea.py>`
+
+
+Verification
+------------
+
+The following go code was used to verify the vectors.
+
+TODO: verify the vectors.
diff --git a/docs/development/custom-vectors/idea/generate_idea.py b/docs/development/custom-vectors/idea/generate_idea.py
new file mode 100644
index 0000000..c8fe7ed
--- /dev/null
+++ b/docs/development/custom-vectors/idea/generate_idea.py
@@ -0,0 +1,59 @@
+import binascii
+
+from cryptography.hazmat.backends.openssl.backend import backend
+from cryptography.hazmat.primitives.ciphers import base, algorithms, modes
+
+
+def encrypt(mode, key, iv, plaintext):
+    cipher = base.Cipher(
+        algorithms.IDEA(binascii.unhexlify(key)),
+        mode(binascii.unhexlify(iv)),
+        backend
+    )
+    encryptor = cipher.encryptor()
+    ct = encryptor.update(binascii.unhexlify(plaintext))
+    ct += encryptor.finalize()
+    return binascii.hexlify(ct)
+
+
+def build_vectors(mode, filename):
+    vector_file = open(filename, "r")
+
+    count = 0
+    output = []
+    key = None
+    iv = None
+    plaintext = None
+    for line in vector_file:
+        line = line.strip()
+        if line.startswith("KEY"):
+            if count != 0:
+                output.append("CIPHERTEXT = {}".format(
+                    encrypt(mode, key, iv, plaintext))
+                )
+            output.append("\nCOUNT = {}".format(count))
+            count += 1
+            name, key = line.split(" = ")
+            output.append("KEY = {}".format(key))
+        elif line.startswith("IV"):
+            name, iv = line.split(" = ")
+            iv = iv[0:16]
+            output.append("IV = {}".format(iv))
+        elif line.startswith("PLAINTEXT"):
+            name, plaintext = line.split(" = ")
+            output.append("PLAINTEXT = {}".format(plaintext))
+
+    output.append("CIPHERTEXT = {}".format(encrypt(mode, key, iv, plaintext)))
+    return "\n".join(output)
+
+
+def write_file(data, filename):
+    with open(filename, "w") as f:
+        f.write(data)
+
+cbc_path = "tests/hazmat/primitives/vectors/ciphers/AES/CBC/CBCMMT128.rsp"
+write_file(build_vectors(modes.CBC, cbc_path), "idea-cbc.txt")
+ofb_path = "tests/hazmat/primitives/vectors/ciphers/AES/OFB/OFBMMT128.rsp"
+write_file(build_vectors(modes.OFB, ofb_path), "idea-ofb.txt")
+cfb_path = "tests/hazmat/primitives/vectors/ciphers/AES/CFB/CFB128MMT128.rsp"
+write_file(build_vectors(modes.CFB, cfb_path), "idea-cfb.txt")
diff --git a/docs/development/test-vectors.rst b/docs/development/test-vectors.rst
index 3b8632e..8b3a646 100644
--- a/docs/development/test-vectors.rst
+++ b/docs/development/test-vectors.rst
@@ -56,7 +56,9 @@
 * CAST5 (ECB) from :rfc:`2144`.
 * CAST5 (CBC, CFB, OFB) generated by this project.
   See: :doc:`/development/custom-vectors/cast5`
-
+* IDEA (ECB) from the `NESSIE IDEA vectors`_ created by `NESSIE`_.
+* IDEA (CBC, CFB, OFB) generated by this project.
+  See: :doc:`/development/custom-vectors/idea`
 
 Creating Test Vectors
 ---------------------
@@ -68,6 +70,7 @@
     :maxdepth: 1
 
     custom-vectors/cast5
+    custom-vectors/idea
 
 If official test vectors appear in the future the custom generated vectors
 should be discarded.
@@ -92,3 +95,5 @@
 .. _`RIPEMD website`: http://homes.esat.kuleuven.be/~bosselae/ripemd160.html
 .. _`Whirlpool website`: http://www.larc.usp.br/~pbarreto/WhirlpoolPage.html
 .. _`Specification repository`: https://github.com/fernet/spec
+.. _`NESSIE IDEA vectors`: https://www.cosic.esat.kuleuven.be/nessie/testvectors/bc/idea/Idea-128-64.verified.test-vectors
+.. _`NESSIE`: https://en.wikipedia.org/wiki/NESSIE