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Frequently Asked Questions
The following Frequently Asked Questions, answered by the authors of this book, are designed to both measure your understanding of the concepts presented in this chapter and to assist you with real-life implementation of these concepts. To have your questions about this chapter answered by the author, browse to www.syngress.com/solutions and click on the “Ask the Author” form. You will alsogain access to thousands ofotherFAQs at ITFAQnet.com.1. | Would I ever need to use XML encryption and XML digital signatures together? |  |
2. | If I do decide to use XML encryption and XML digital signatures together, should I sign the document and then apply encryption, or encrypt the document and then sign it? | |
3. | If I need to encrypt my entire document and don’t intend to archive my document, wouldn’t I be better off sending the document through SSL? | |
4. | Which algorithms and key size do you recommend for XML encryption and XML digital signatures? | |
Answers
1. | Encrypted data cannot be modified undetected, so XML encryption also provides the data integrity benefit of a digital signature. XML encryption, however, does not require the use of asymmetrical encryption (private and public keys). Asymmetrical encryption is the technology that provides the benefit of authentication and nonrepudiation. If your needs require privacy, integrity, authentication, and nonrepudiation, you need to use them together. |
2. | Both methods will work, and there is currently no standard specifying which to do first. It is critical, however, that the document recipient knows the order in which the encryption and signature were applied; otherwise, the recipient will not be able to generate the correct hash of the document. |
3. | Yes, if you are satisfied with the SSL algorithm and key size. In this case, the benefit of utilizing XML encryption is that it allows you to specify your own algorithm and key size. |
4. | See Chapter 4 for a thorough discussion on the strengths of various algorithms and recommended key sizes for each. |
