The structure of the Message depends on whether the SecurityPolicy requires an algorithm that combines encryption and authentication (e.g. Authenticated Encryption algorithms) used or if it requires separate algorithms for each operation (Unauthenticated Encryption algorithms).
Figure 11 shows the structure of a MessageChunk and how security is applied to the Message when using Unauthenticated Encryption algorithms. For these SecurityPolicies any padding is appended to the message before appending the Signature.
Figure 12 shows the structure of a MessageChunk and how security is applied to the Message when using Authenticated Encryption algorithms. For these SecurityPolicies the Signature is calculated during encryption and appended after the encrypted data. Padding is not needed.