Lemma round13_eq_assemble: forall buf plaintext S0 S12 S13, S0 = mbed_tls_initial_add_round_key plaintext buf -> S12 = mbed_tls_enc_rounds 12 S0 buf 4 -> S13 = mbed_tls_fround S12 buf 52 -> S13 = mbed_tls_enc_rounds 13 (mbed_tls_initial_add_round_key plaintext buf) buf 4.