Which of the following can be best defined as computing techniques for inseparably embedding unobtrusive
marks or labels as bits in digital data and for detecting or extracting the marks later?

A.
Steganography

B.
Digital watermarking

C.
Digital enveloping

D.
Digital signature

Explanation:
Digital watermarking is defined as “Computing techniques for inseparably embedding unobtrusive marks or
labels as bits in digital data — text, graphics, images, video, or audio — and for detecting or extracting the marks
later.”
A “digital watermark”, i.e., the set of embedded bits, is sometimes hidden, usually imperceptible, and always
intended to be unobtrusive. Depending on the particular technique that is used, digital watermarking can assist
in proving ownership, controlling duplication, tracing distribution, ensuring data integrity, and performing other
functions to protect intellectual property rights.
Incorrect Answers:
A: Steganography is a method of hiding data in another media type so the very existence of the data is
concealed. Digital Watermarking is considered to be a type of steganography. However, steganography is not
what is described in the question.
C: A digital envelope is another term used to describe hybrid cryptography where a message is encrypted with
a symmetric key and the symmetric key is encrypted with an asymmetric key. This is not what is described in
the question.
D: A digital signature is a mathematical technique used to validate the authenticity and integrity of a message,
software or digital document. This is not what is described in the question.

http://tools.ietf.org/html/rfc4949