diff --git a/LICENSE b/LICENSE
index d3998e2ad183db4a7d8d6ea4130557334e3771f9..e452190d7ca767dd7f24e3a5e7fcaae983afa197 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2019 Gaëtan Cassiers
+Copyright (c) 2019, 2020 Gaëtan Cassiers
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/README.md b/README.md
index daeac0d1ea480fdc88dea53cf697ea7d49ef7da0..59673328a1973f827cdf5b9f0762081e05cbe3bb 100644
--- a/README.md
+++ b/README.md
@@ -12,3 +12,9 @@ The `spook_encrypt` and `spook_decrypt` functions take as input bytes objects. T
 ## License
 
 This software distributed under the terms of the MIT license. See [LICENSE](LICENSE) for details.
+
+## Changelog (see git log for details)
+
+- `v1.0` Initial version
+- `v2.0` Remove the `p` parameter from the API to match the NIST API.
+
diff --git a/spook.py b/spook.py
index e59b58619066ce784a4ce3dd14ec171e2b172e04..b58fe073d7217bb0d19fd595c1518200342d83e8 100644
--- a/spook.py
+++ b/spook.py
@@ -1,6 +1,6 @@
 # MIT License
 #
-# Copyright (c) 2019 Gaëtan Cassiers
+# Copyright (c) 2019, 2020 Gaëtan Cassiers
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -38,6 +38,8 @@ Implementation details:
     of LS states.
 """
 
+__version__= '2.0'
+
 SMALL_PERM=False
 N_STEPS=6
 
@@ -188,14 +190,15 @@ def shadow(x):
 def pad_bytes(b,n=LS_SIZE):
     return b.ljust(n, bytes((0,)))
 
-def init_sponge_state(k, p, n):
-    if p:
-        assert len(p) == 16
-        p = bytearray(p)
+def init_sponge_state(k, n):
+    if len(k) == 32:
+        # mu variant
+        p = bytearray(k[16:])
         p[-1] &= 0x7F
         p[-1] |= 0x40
         p = bytes2state(p)
     else:
+        assert len(k) == 16
         p = (0, 0, 0, 0)
     n = bytes2state(n)
     b = clyde_encrypt(n, p, bytes2state(k))
@@ -239,8 +242,8 @@ def compress_data(x, data, mode='ENC'):
         x = shadow(x)
     return x, res
 
-def spook_encrypt(ad, m, k, p, n):
-    x = init_sponge_state(k, p, n)
+def spook_encrypt(ad, m, k, n):
+    x = init_sponge_state(k, n)
     x, _ = compress_data(x, ad)
     if m:
         x[-2][0] ^= 0x1
@@ -251,8 +254,8 @@ def spook_encrypt(ad, m, k, p, n):
     tag = state2bytes(clyde_encrypt(x[0], x[1], bytes2state(k)))
     return c+tag
 
-def spook_decrypt(ad, c, k, p, n):
-    x = init_sponge_state(k, p, n)
+def spook_decrypt(ad, c, k, n):
+    x = init_sponge_state(k, n)
     x, _ = compress_data(x, ad)
     if len(c) > LS_SIZE:
         x[-2][0] ^= 0x1
diff --git a/test.py b/test.py
index f1535e94187299060c35c4bae1a357665225e2a1..9fc1b9c65f82a4cfa2be3a69f332f4d7cf872267 100644
--- a/test.py
+++ b/test.py
@@ -3,16 +3,13 @@
 import spook
 
 def test_spook_lwc(ad, m, k, n, c):
-    p = k[16:]
-    k = k[:16]
     print('AD', ad)
     print('M', m)
     print('k', k)
-    print('p', p)
     print('n', n)
     print('c', c)
-    c2 = spook.spook_encrypt(ad, m, k, p, n)
-    m2 = spook.spook_decrypt(ad, c2, k, p, n)
+    c2 = spook.spook_encrypt(ad, m, k, n)
+    m2 = spook.spook_decrypt(ad, c2, k, n)
     assert m2 == m, 'wrong inverse {} {}'.format(m, m2)
     assert c2 == c, 'not matching TV {} {}'.format(c, c2)