Before delving into the world of digital data, it is essential to understand several key terms. This glossary will be updated regularly.

Metadata

Electronic documents often contain more information than meets the eye. Metadata is data about data; embedded information that does not appear in a printed version of an electronic document. Examples of metadata includes prior revisions to word processing documents, the identity of blind copied individuals on e-mail messages, and internet usage histories. Metadata is an important element in law enforcement and litigation in the electronic age.

Bytes, Kilobytes and Gigabytes

Bit: The smallest unit of information on a computer. Bit is short for the term binary digit and can only consist of the numbers 0 or 1. Bits are used in various combinations of the numbers 0 and 1 to create meaningful information, such as a byte.

Byte: A computer storage unit containing enough memory to hold a store a single character, such as a number or a letter. A Byte is composed of eight bits.

Because bytes are a small unit, it is more common to see the terms kilobytes and gigabytes to refer to storage space on a computer.

Kilobyte: 1,024 bytes

Megabyte: 1,048,576 bytes or 1,024 kilobytes

Gigabyte: 1,073,741,824 bytes or 1,024 megabytes

Types of Data

Active, Online Data: Active data is usually stored on magnetic discs, such as hard drives.  Active data is data that is presently in use or is accessed frequently. It is the simplest data to obtain.

Near-line Data: Data that is stored using a robotic storage device, which employs robotic arms to access media. Optical discs are one example of near-line data.

Offline Storage/archives: Data that is stored in a removable form of media, such as a removable optical disc or magnetic tape, that can be stored on a shelf outside of the computer. Frequently, offline storage is used to make disaster copies or to store data that is not accessed often.

Backup Tapes: Devices that record data and write it onto tapes. Backup tapes have significant storage capacity of up to several gigabytes. Data is not organized by file, making recovery of documents from back up tapes both time-consuming and expensive.

Erased, Fragmented or damaged Data: When data is saved to a computer, it is stored in contiguous clusters. As each file is erased, those clusters become open space. As the remaining files grow, they can expand beyond the contiguous space available on the hard drive. When the files outgrow the space, they are broken up, or fragmented, and the fragments are placed randomly throughout the hard drive. Fragmented, erased or damaged data can only be accessed using computer forensics. Erased data is not truly deleted from the hard drive until the computer writes over the erased data.

Types of Encryption

Encryption: Encryption is a method of protecting data by translating it into a secret code.  Encrypted data is sometimes referred to as cypher text as opposed to unencrypted plain text.  To read an encrypted document, one must have either a key or password to decrypt it. There are two general categories of encrypted data: symmetrical and asymmetrical.

Asymmetrical Encryption: Also called public-key encryption. This system uses a public key and a private key to encrypt data. The intended recipient of an encrypted message can provide his or her public key to the individual sending the message. The sender then uses the public key to encrypt the message. The private key is held only by the intended recipient. In essence, the public key is used to lock the data and the private key is used to unlock the data. It is impossible to decrypt the data without the private key. Pretty Good Privacy (PGP) is a widely used encryption tool in the United States.

Symmetrical Encryption: Like asymmetrical encryption, this system uses keys to encrypt and decrypt messages. However, rather than using two separate keys, the same key is used to encrypt and decypher the message.

Native Data/ Native Form: The original form of data, as it is used in its ordinary course. Example: a Microsoft Excel document that has not been cleaned of metadata or reformatted to PDF, JPEG or TIFF. FRCP Rule 34(b) allows the party requesting electronic data to specify the form of production, such as metadata or native data.