While cryptography is about protecting the content of messages (their meaning), steganography is about concealing their very existence. It comes from Greek roots, literally means 'covered writing', and is usually interpreted to mean hiding information in other information. Examples include sending a message to a spy by marking certain letters in a newspaper using invisible ink, and adding sub-perceptible echo at certain places in an audio recording.

Cryptography is the science of enabling secure communications between a sender and one or more recipients. This is achieved by the sender scrambling a message (with a computer program and a secret key) and leaving the recipient to unscramble the message (with the same computer program and a key, which may or may not be the same as the sender's key). The emphasis of cryptography is on data confidentiality, data integrity, sender authentication, and non-repudiation of origin/data accountability. See similar questions...

There are a few good resources available that should be able to help you better understand cryptography, regardless of your level of experience. Some of these can get quite technical, so if you're looking for a quicker introduction to some of the concepts and such, you'll probably want to grab the Snake Oil FAQ which was written to be understandable by an IS-type person without lots of background in mathematics or information security. See similar questions...

Watermarking is an embedded signal that applies a digital signature in the form of noise (supposedly inaudible) on a DVD-A. In a proposed, but never implemented, extension to this system, the digital watermark would actually put a faint image (either text or graphics) on the signal side of the disc that makes it extremely hard for pirates to duplicate. The watermark would also identify the artist, record company, catalog number and copyright holder. See similar questions...

Encryption is the transformation of data into a form (a cipher) that is, for most intents and purposes, impossible to read with out the appropriate decoder (a cryptographic key). Its purpose is to ensure privacy by keeping information hidden from anyone for whom it is not intended, even those who have access to the encrypted data. Decryption is the reverse of encryption; it is the transformation of encrypted data back into an intelligible form. See similar questions...

A digital watermark is an imperceptible signal hidden in an audio clip, or an image, or any other object of value. The hidden signal is intended to communicate information about the marked object. There are many applications of watermarking. In the context of SDMI, the application is screening and piracy prevention: an audio clip with a watermark is recognized as copyrighted, warning a portable device that it should not be recorded (or possibly even played) except under specific conditions. See similar questions...

We will discuss these in detail in our upcoming technical report. Briefly, challenge D concerned a method for preventing people from ripping tracks from a CD, unless that CD has a signature on it marking the CD as original. Thus, as far as we can tell, this is intended to allow you to make mix CDs and MP3s from your original CDs, but not permit you to make mixes and MP3s from other mix CDs or pirated CDs. See similar questions...

Digital watermarking is the process by which identifying data is woven into media content such as images, movies, music or programming, giving those objects a unique, digital identity that can be used for a variety of valuable applications. See similar questions...

The story begins: When Julius Caesar sent messages to his trusted acquaintances, he didn't trust the messengers. So he replaced every A by a D, every B by a E, and so on through the alphabet. Only someone who knew the ''shift by 3 rule could decipher his messages. A cryptosystem or cipher system is a method of disguising messages so that only certain people can see through the disguise. Cryptography is the art of creating and using cryptosystems. See similar questions...

Secret-key cryptography is sometimes referred to as symmetric cryptography. It is the more traditional form of cryptography, in which a single key can be used to encrypt and decrypt a message. Secret-key cryptography not only deals with encryption, but it also deals with authentication. See similar questions...

Public Key Cryptography is a method for securely exchanging messages, based on assigning two complimentary keys (one public, one private) to the individuals involved in a transaction. Public Key Cryptography is based on the science of encryption, the mathematical scrambling and unscrambling of messages. See similar questions...

Cryptography has many applications on the internet today, from the protection of documents to the securing of online transactions. The following sites offer additional information: Handbook of Applied Cryptography See similar questions...

Secret key (symmetric/conventional) cryptography is a system based on the sender and receiver of a message knowing and using the same secret key to encrypt and decrypt their messages. One weakness of this system is that the sender and receiver must trust some communications channel to transmit the secret key to prevent from disclosure. Example: You use a strongbox to send a valuable gift to your friend, locking it with a key. No one can get to the gift without the key, including your friend. See similar questions...

Public key (asymmetric) cryptography is a system based on pairs of keys called public key and private key. The public key is published while the private key is kept secret with the owner. The need for a sender and a receiver to share a secret key and trust some communications channel is eliminated. This concept was introduced in 1976 by Whitfield Diffie and Martin Hellman. See similar questions...

No! Watermarking has a lot of different applications, and a lot of potential. Any successful hack of SDMI's watermarking technologies is due to the particular application of watermarking they had in mind, and the way they intended to integrate it into a security system. See similar questions...

Most watermarking will work properly with MIS. Most watermarking is digitally interleaved into the image prior to mastering. Therefore MIS simply passes it through to the LBR untouched. Top DCA has verified that Plaxtor has discontinued its 40Max SCSI CD-Rom drive. This is part of a larger strategy by Plextor to stop manufacturing read only SCSI drive support. See similar questions...