Blue-ray disc (BD) is a next generation optical disc format meant for storage of high definition video and high –density data. As compared to the HDVD format, its main competitor, Blu-ray has more information capacity per layer, 25 instead of 15 gigabytes. Blu-ray dics not only have more storage capacity than traditional DVDs, but they also offer a new level of interactivity. Users will be able to connect to the internet and instantly download subtitles and other interactive movie features.

Blu-ray gets its name from the shorter wavelength (405 nm) of a “blue” (technically blue-violet) laser that allows it to store substantially more data than a DVD, which has the same physical dimensions but uses a longer wavelength(650 nm red laser).

There are plans for BD-ROM (read only), BD (recordable) and BD-RE (rewritable) drives for PCS and with the support of the manufacturers, it’s very likely that the technology will be adopted as the next-generation optical disc format for PC data storage and replace technologies such as DVD+-R, DVD+-RW, and DVD+-RAM.

INTRODUCTION TO BLUE-RAY DISC

A current, single-sided, standard DVD can hold 4.7 GB (gigabytes) of Information. That's about the size of an average two-hour, standard-definition movie with a few extra features. But a high-definition movie, which has a much clearer image (see how Digital Television Works), takes up about five times more bandwidth and therefore requires a disc with about five times more storage. As TV sets and movie studios make the move to high definition consumers are going to need playback systems with a lot more storage capacity.

Photo courtesy BIu-ray Disc Association BD-ROM disc researcher

Blu-ray is the next-generation digital video disc. It can record, store and play back high definition video and digital audio, as well as computer data.

The advantage to BIu-ray is the sheer amount of information it can hold:

· A single-layer BIu-ray disc, which is roughly the same size as a DVD, can hold up to 27 GB of data that's more than two hours of high-definition video or about 13 hours of standard video.

· A double-layer Blu-ray disc can store up to 54 GB, enough to hold about 4.5 hours of high-definition video or more than 20 hours of standard video ..

ADVANTAGES OF BLU_RAY DISC:

· Record High-Definition Television (HDTV) without any quality loss.

· Instantly skip to any spot on the disc.

· Record one program while watching another on the disc

· Create play lists.

· Edit programs recorded on the disc.

· Automatically search for an empty space on the disc to avoid recording over a program.

· Access the web to down load subtitles and other extra features

WORKING OF BLU_RAY:

Discs store digitally encoded video and audio information in pits spiral grooves that run from the center of the disc to its edges. A laser reads the other side of these pits the bumps to play the movie or program that is stored on the DVD. The more data that is contained on a disc, the smaller and more closely packed the pits must be. The smaller the pita (and therefore the bumps), the more precise the reading laser must be.

Unlike current DVD’s, which use a red laser to read and write data, Blu-ray uses a blue laser (which is where the format gets its name). A blue laser has a shorter wavelength (405 nanometers) than a red laser (650 nano meters). The smaller beam focuses more precisely, enabling it to read information recorded in pits that are not only 0.15 microns long this is more than twice as small as the pits on a DVD.Plus, Blue-ray has reduced the track pitch from 0.74 microns to 0.32 microns. The smaller pits, smaller beam and shorter track pitch together enable a single-layer Blu-ray disc to hold more than 25GB of information about five times the amount of information that can be stores on a DVD.

Each BIu-ray disc is about the same thickness (1.2 millimeters) as a DVD. But the two types of discs store data differently. In a DVD, the data is sandwiched between two polycarbonate layers, each O.6-mm thick. Having a polycarbonate layer on top of the data can cause a problem called birefringence, in which the substrate layer refracts the laser light into two separate beams. If the beam is split too widely, the disc cannot be read. Also, if the DVD surface is not exactly flat, and is therefore not exactly perpendicular to the beam, it can lead to a problem known as disc tilt, in which the laser beam is distorted. All of these issues lead to a very involved manufacturing process.

BUILDING OF BLU-RAY:

The BIu-ray disc overcomes DVD-reading issues by placing the data on top of a l.l-mmthick polycarbonate layer. Having the data on top prevents birefringence and therefore prevents readability problems. And, with the recording layer sitting closer to the objective lens of the reading mechanism, the problem of disc tilt is virtually eliminated. Because the data is closer to the surface, a hard coating is placed on the outside of the disc to protect it from scratches and fingerprints.

The design of the BIu-ray discs saves on manufacturing costs. Traditional DVDs are built by injection molding the two O.6-mm discs between which the recording layer is sandwiched. The process must be done very carefully to prevent birefringence.

1. The two discs are molded.

2. The recording layer is added to one of the discs.

3. The two discs are glued together.

BIu-ray discs only do the injection-molding process on a single I.I-mm disc, which reduces cost. hat savings balances out the cost of adding the protective layer, so the end price is no more than the price of a regular DVD.

BLU-RAY VS OTHER NEW DISC FORMATS:

Will Blu-ray replace previous DVDs? Its manufactures hope so. In the meantime JVC has developed a Blu-ray /DVD combo disc with an approximate 33.5GB capacity, allowing for the release of video in both formats on a single disc. But Blu-ray is not alone in the marketplace. A few other formats are competeting for a share of DVD market.

HD-DVD:

The other big player is HD_DVD, also called AOD(Advanced Optical Disc), which DVD and can therefore be manufactured with the same equipment, saving on costs. The disadvantage is that it can’t match the storage capacity of Blu-ray. A rewritable, single layer HD_DVD can hold 20 GB of data; a double –layer disc can hold 30 GB(that’s compared to 27 GB and 50 GB for Blu-ray). The read-only versions hold slightly less data. Also, HD_DVD doesn’t offer the interactive capabilities of Blu-ray , although it will probably be less expensive than its competitor

OTHER COMPETETORS:

Blu-ray and HD-DVD are the two major competitors in the market, there are other contenders, as well. Warner Bros. Pictures has developed its own system, called HD-DVD-9. This system uses a higher compression rate to put more information (about two hours of high –definition video) on a standard DVD. Taiwan has created the Forwarded Versatile Disc(FVD), an upgraded version of today’s DVDs that allows for more data storage capacity (5.4 GB on a single –sided disc and 9.8 GB on a double-sided disc). And China has introduced the Enhanced Video Disc (EVD), another high-defnition video disc

There are also professional versions of the Blu laser technology. Sony has developed XDCAM and ProData (Professional Disc for Data). The former is designed for use by broadcasters and AV studios. The latter is primarily for commercial data storage (for example ,backing up servers).

Blu-ray recorders are already available in Japan, where more consumers have access to HDTV than in the United States. Outside of Japan, once more TV sets come equipped with a high-definition tuner and more films and television shows are produced in high-definition ( which is expected to happen by late 2005 or 2006), BIu-ray movies and TV shows on disc should become widely available. But the format is already available for home recording, professional recording and data storage.

Another important factor is cost. Just as with most new technologies, Blu-ray equipment will be pricey at first. In 2003, Sony released its first BIu-ray recorder in Japan with a price tag of around $3,000. The price is expected to drop as the format gains popularity. Blu-ray discs may also be initially more expensive than today's DVDs, but once demand grows and they can be mass-produced, manufacturers say the price will drop to within 10 percent of the price of current DVDs.

Even when the new video standard begins to replace current technologies, consumers won't have to throw away their DVDs, but they will need to invest in a new player. The industry is planning to market backward-compatible drives with both blue and red lasers, which will be able to play traditional DVDs and CDs as well as Blu-ray discs.

APPLICA TIONS:

The Play station 3 will be the first Blu-ray accessable player.

The first BIu-Ray recorder was unveiled by Sony and was introduced to the Japanese market. JVC and Samsung Electronics announced Blu-ray based products at IFA in Berlin, Germany.

Sony has announced that the PlayStation 3 will be shipped with a Blu-Ray drive, but possibly just a read-only one. Sony's machine will also support BD-ROM pre-recorded media, which are expected to be available in early 2006.

PC DATA STORAGE

Blu-ray drives currently in production can transfer approximately 36 Mbit/s (54 Mbit/s for BD-ROM), but 2x speed prototypes with a 108 Mbit/s transfer rate are in development. Rates of 8x or more are planned for the future.

Hewlett Packard has announced plans to sell Blu-ray-equipped desktop PCs and laptops. In December 2005, HP announced that they would also be supporting the rival HD DVD technology. Philips was scheduled to debut a Blu-ray computer drive in the second half of 2005, but it was also delayed. On March 10, 2005 Apple Computer joined the Blu-ray Disc Association.

CONCLUSION:

Blu-ray disc has been a consistent road map to emerging disc technologies. Blue-ray can store up to 54 GB, enough to hold about 4.5 hours of high -definition video or more than 20 hours of standard video. And there are even plans in the works to develop a disc with twice that amount of storage.

It’s very likely that the technology will be adopted as the next generation optical disc format for PC data storage and replace technologies such as DVD+-R, DVD+-RW, and DVD-RAM.

REFERENCES:

TEXT BOOKS:

1. Complete Guide to Digital Audio By—Chris Middleton.

2. The Digital Bits Insider Guide to DVD By—Bill Hunt

3. DVD Demystified By – Jim Taylor

WEBSITES:

1. www.howstuffworks.com

2. www.blue-ray.com

Cryptography and Network Security

Does security provide some very basic protections that we are naive to believe that we don't need? During this time when the Internet provides essential communication between tens of millions of people and is being increasingly used as a tool for commerce, security becomes a tremendously important issue to deal with. There are many aspects to security and many applications, Ranging from secure commerce and payments to private Communications and protecting passwords. One essential aspect for Secure communications is that of cryptography.

Cryptography is the science of writing in secret code and is an ancient art. The first documented use of cryptography in writing dates back to circa 1900 B.C. when an Egyptian scribe used non-standard hieroglyphs in an inscription.

In data and telecommunications,cryptography is necessary when communicating over any untrusted medium, which includes just about any network, particularly the Internet.Within the context of any application-to-application communication, there are some specific security requirements, including:

Authentication: The process of proving one's identity. (The primary forms of host-to-host authentication on the Internet today are name-based or address-based, both of which are notoriously weak.)

· prrivacy/confidentiality: Ensuring that no one can read the message except the intended receiver.

· Integrity: Assuring the receiver that the received message has not been altered in any way from the original.

· Non-repudiation: A mechanism to prove that the sender really sent this message. Cryptography, then, not only protects data from theft or alteration, but can also be used for user authentication.

· The three types of cryptographic algorithms that will be discussed are (Figure 1):

· Secret Key Cryptography (SKC): Uses a single key for both encryption and decryption Public Key Cryptography (PKC): Uses one key for encryption and another for decryption

· Hash Functions: Uses a mathematical transformation to irreversibly "encrypt" information

1. Secret Key Cryptography

With secret key cryptography, a single key is used for both encryption and decryption.

As shown in Figure the sender uses the key (or some set of rules) to encrypt the plain text and sends the cipher text to the receiver. The receiver applies the same key (or rule set) to decrypt the message and recover the plain text. Because a single key is used for both functions, secret key cryptography is also called symmetric encryption.

With this form of cryptography, it is obvious that the key must be known to both the sender and the receiver; that, in fact, is the secret. The biggest difficulty with this approach, of course, is the distribution of the key.Secret key cryptography schemes are generally categorized as being either stream ciphers or block ciphers.

Stream ciphers operate on a single bit (byte or computer word) at a time and implement some form of feedback mechanism so that the key is constantly changing. A block cipher is so- called because the scheme encrypts one block of data at a time using the same key on each block. In general, the same plain text block will always encrypt to the same cipher text when using the same key in a block cipher whereas the same plaintext will encrypt to different cipher text in a stream cipher.

2. Public key cryptography

Modern PKC was first described publicly by Stanford University professor Martin Hellman and graduate student Whitfield Diffie in 1976. Their paper described a two-key crypto system in which two parties could engage in a secure communication over a non-secure communications channel without having to share a secret key. Generic PKC employs two keys that are mathematically related although knowledge of one key does not allow someone to easily determine the other key. One key is used to encrypt the plaintext and the other key is used to decrypt the cipher text. The important point here is that it does not matter which key is applied first, but that both keys are required for the process to work (Figure 1B). Because a pair of keys are required, this approach is also called asymmetric cryptography

3. Hash Functions

Hash functions, also called message digests and one-way encryption, are algorithms that, in some sense, use no key (Figure 1C). Instead, a fixed-length hash value is computed based upon the plaintext that makes it impossible for either the contents or length of the plaintext to be recovered. Hash algorithms are typically used to provide a digital fingerprint of a file's contents often used to ensure that the file has not been altered by an intruder or virus. Hash functions are also commonly employed by many operating systems to encrypt passwords. Hash functions, then, help preserve the integrity of a file.

4. TRUST MODELS

Secure use of cryptography requires trust. While secret key cryptography can ensure message confidentiality and hash codes can ensure integrity, none of this works without trust. In SKC, PKC solved the secret distribution problem. There are a number of trust models employed by various cryptographic schemes.

· The web of trust employed by Pretty Good Privacy (PGP) users, who hold their own set of trusted public keys.

· Kerberos, a secret key distribution scheme using a trusted third party.

· Certificates, which allow a set of trusted third parties to authenticate each other and, by implication, each other's users.

Each of these trust models differs in complexity, general applicability, scope, and scalability.

Types of authority

· Establish identity: Associate, or bind, a public key to an individual, organization, corporate position, or other entity.

· Assign authority: Establish what actions the holder may or may not take based upon this certificate.

· Secure confidential information (e.g., encrypting the session's symmetric key for data confidentiality).

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Todays latest used cryptographic techniques:Hash algorithms that are in common use today include:Message Digest (MD) algorithms

v Secure Hash Algorithm (SHA)

Pretty Good Privacy (PGP)

Pretty Good Privacy (PGP) is one of today's most widely used public key cryptography programs. PGP can be used to sign or encrypt e-mail messages with mere click of the mouse.

Depending upon the version of PGP, the software uses SHA or MD5 for calculating the message hash; CAST, Triple-DES, or IDEA for encryption; and RSA or DSS/Diffie-Hellman for key exchange and digital signatures. And much more techniques used.

Time is the only true test of good cryptography; any cryptographic scheme that stays in use year after year is most likely a good one. The strength of cryptography lies in the choice (and management) of the keys; longer keys will resist attack better than shorter keys

Encrypt and decrypt messages using any of the classical substitution ciphers discussed, both by hand and with the assistance of programs.

understand the concepts of language redundancy and unicity distance.

Different types of threats to network:

· Application backdoors - Some programs have special features that allow for remote access . Others contain bugs that provide a backdoor , or hidden access , that provides some level of control of the program.

· SMTP session hijacking - SMTP is the most common method of Sending e-mail over the Internet . By gaining access to a list of e- mail Addresses , a person can send unsolicited junk e-mail ( spam ) to thousands of users . This is done quite often by redirecting the e-mail through the SMTP server of an unsuspecting host , making the actual sender of the spam difficult to trace.

· Operating system bugs - Like applications , some operating systems Have backdoors . Others provide remote access with insufficient security controls or have bugs that an experienced hacker can take advantage of .

· Denial of service - You have probably heard this phrase used in news reports on the attacks on major Web sites . This type of attack is nearly Impossible to counter . What happens is that the hacker sends a request to the server to connect to it . When the server responds with an acknowledgement and tries to establish a session , it cannot find the system that made the request . By inundating a server with these unanswerable session requests , a hacker causes the server to slow to a crawl or eventually crash.

· E-mail bombs - An e-mail bomb is usually a personal attack . Someone sends you the same e-mail hundreds or thousands of times until your e-mail system cannot accept any more messages .

· Macros - To simplify complicated procedures , many applications allow you to create a script of commands that the application can run . This script is known as a macro . Hackers have taken advantage of this to create their own macros that , depending on the application , can destroy your data or crash your computer .

· Viruses - Probably the most well-known threat is computer viruses . A virus is a small program that can copy itself to other computers . This way it can spread quickly from one system to the next. Viruses range from harmless messages to erasing all of your data .

· Spam - Typically harmless but always annoying , spam is the electronic equivalent of junk mail . Spam can be dangerous though . Quite often it contains links to Web sites . Be careful of clicking on these because you may accidentally accept a cookie that provides a backdoor to your computer.

· Redirect bombs - Hackers can use ICMP to change ( redirect ) the Path information takes by sending it to a different router . This is one of the ways that a denial of service attack is set up.

Network security can be done by various methods.

1. Virtual Private Network:

A virtual private network ( VPN ) is a way to use a public telecommunication infrastructure , such as the Internet , to provide remote offices or individual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same capabilities , but at a much lower cost

Implementation of network security by VPN.

Step 1. - The remote user dials into their local ISP and logs into the ISP’s network as usual.

Step 2. - When connectivity to the corporate network is desired, the user initiates a tunnel request to the destination Security server on the corporate network. The security server authenticates the user and creates the other end of tunnel.

Fig : a) A leased line private network b) A virtual private network

Step 3. - The user then sends data through the tunnel which encrypted by the VPN software before being sent over the ISP connection.

Step 4. - The destination Security server receives the encrypted data and decrypts. The Security server then forwards the decrypted data packets onto the corporate network. Any information sent back to the Remote user is also encrypted before being sent over the Internet.