LGTM, minor comment below. https://codereview.appspot.com/54690045/diff/1/src/python/ct/crypto/cert_test.py File src/python/ct/crypto/cert_test.py (right): https://codereview.appspot.com/54690045/diff/1/src/python/ct/crypto/cert_test... src/python/ct/crypto/cert_test.py:171: def test_identical(self): Nit: It's now considered good practice to separate these groups of assertions to separate unit tests