Have you ever wondered what exactly a Credstick is, and how is works?

A NOTE ON ACRONYMS
Each of the features of a credstick depends on a certain type of chip storage, access and permanence. Credsticks use three distinct flavors of optical chip:

RAM: Random Access Memory. This chip is effectively an array of holes which can be filled and unfilled with data. The data they hold is kept there until it is changed or removed. In older days (pre-2000) RAM usually had to have a constant source of power to maintain its data; in the 60's, this is no longer the case. RAM is what is usually referred to when talking about computer 'memory'. Of the three type of chips in a credstick, RAM is the most transitory, in that it is the only type of chip which has user-erasable data.
ROM: Read Only Memory. This is a chip which has its data burned into it during its construction. It cannot be altered by any means save destruction. These types of chips are used to hold code that is unalterable by users, or data that the manufacturer does not want altered.
WORM: Write Once, Read Many. These chips are a step between ROM and RAM. These chips come from the factory blank and data may be written on them; however, writing data to a WORM chip is a destructive process (holes are burned into the chip), which means that once part of a WORM chip has been written to, that portion becomes unalterable and unerasable. An analogy is a stone tablet, which once it has been carved into is marred for life. To strike a balance between cost and security, most chips in a credstick are of this type.

SPECIFICATIONS

Dimensions: 6cm long, 0.5cm radius at the base.
Weight: 7g 
Styles:     Maximum Amount    Minimum ID Level      Bands 
Standard         5,0004Ą      Passcode             1 Green 
Silver          20,0004Ą      Fingerprint          2 Silver 
Gold           200,0004Ą      Voiceprint           3 Gold 
Platinum     1,000,0004Ą      Retinal Scan         4 Silver 
Ebony        unlimited Ą      Cellular Scan        5 Black

Appearance: Cylindrical hard plastic cone; thin. The last centimeter of the point is transparent plastic, striped vertically with conductive metal. Colored rings (1.5mm thick) around the fatter end indicate the level of the credstick; the level is indicated both by the color of the band(s) as well as the number of bands present. The rest of the surface of the credstick is generally covered with whatever the bank which issued the stick chose (typically, the name and emblem of the bank, with perhaps some regional imagery). Many banks choose a flat matte black for elegance and anonymity. Certified credsticks are somewhat larger (8cm long) with a display in along the edge indicating how much credit is on the stick. Normal credsticks have no display of their own.

USE
When making a purchase with any credstick, the stick must be inserted into a slot near the register. They purchaser must then verify her identity by entering her passcode and any other ID verification. Note that the level of ID check which is required depends on the amount of the purchase as much as it does on the level of the credstick; most stores have only the ID verification systems most suited to their target market. For example, the owner of an Ebony stick would have to enter only her passcode at a Stuffer Shack but while buying a car, she would have to pass at least a passcode/fingerprint/voiceprint scan, and while buying a new boat, might have to pass all five levels of ID check. Once entered, the Credstick Verification System (CVS) compares the entered information to that encoded onto the credstick. If the entered passcode matches the one on the credstick (and finger/voice/retina/cell patterns come near enough to matching) the CVS check if the current balance of the credstick is enough to pay for the purchase.

Note that at this point, the CVS has taken the credsticks word that all is OK. Next, the CVS gets the Matrix address of the bank from the credstick and connects to it. It now makes two checks, both based upon the fact that the bank has the same identification information as the credstick. First, it verifies that the data which was input to the verifiers matches the banks patterns. This check should almost always turn up the same way that the comparison to the data in the credstick did. Secondly, the patterns in the bank and the credstick are compared; these should always be exactly the same.

If nothing goes wrong, the money is transferred and the bank and the credstick are updated. Lastly, the credstick and the bank confirm that they have updated correctly.

CONSTRUCTION & FUNCTIONS Inside the plastic casing are a very small battery, one ROM chip, three RAM chips, four WORM chips, a small microprocessor and the connections between them. These provide features as follows:

FCP (Fuchi Credstick Processor): This is a very small, limited processor which controls the read/write functions of all the chips. It can pass control off to hard-coded routines on other special chips (like the SCTP ROM, below) for more advanced functions (like handshaking I/O).
SCTP ROM (Standard Credstick Transfer Protocol): This read-only chip contains routines which control the communications with CVS units. It was built with the other chips in the credstick in mind and can be given full control of the credstick.
Eveready CS Rechargeable Battery: This is a very small power source which exists only to allow credstick to credstick transfers. It has a very short life span, but gets fully recharged whenever slotted into a CVS. Except when powering stick-to-stick transfers, the battery provides no power to any chips; normal transfers are powered by the CVS.
KeyRAM: This RAM chip (2Mp) contains key-encrypted keys to locks of the owner of the credstick. The key to the typical lock is a 73 digit number (which generally isn't known to anyone or anything but the lock and the key). When first set up, the credstick is inserted into a new maglock and ID confirmation is downloaded. The lock then writes the key which will open it to this chip. The lock also writes a flag, marking the key as a key to that lock in a way that only the lock will understand. The lock then encrypts the key using a key that only the lock knows. Later, when the user tries to unlock the door and ID is verified, the lock decrypts the key, compares it to its known key and opens that door.
IndentityMatrix(tm): All identity verification information (password, voiceprint, fingerprint) is contained on this 10Mp WORM chip along with the owners name, SIN, photo and vital statistics (including MedicAlert information). The decision to make this a WORM chip rather than a ROM chip is that banks would have the ability to instantly update -- but not alter -- the credsticks of their customers. When a credstick is issued, the issuing bank will record and verify the owners information up to the level needed by the stick; when satisfied that the data is 100%, they write onto the WORM chip. Later, the owner can have his credstick upgraded by writing extra data to the unused portion of the chip; however, old data cannot be corrected or replaced.
Tyr5: This is a 1Mp WORM chip which keeps licensing information of the owner. It functions like the ID chip, but it written to by licensing bureaus like the Department of Motor Vehicles and the Department of Fish and Wildlife. Flags indicating license renewal may be written in later. Each license has an encrypted flag which serves as a seal of the license issuer.
IP10 (International Passport): A 10Mp WORM chip which holds the passport of the owner (if any) and the cumulative 'stamps' of any and all border crossings made by the user.
BNK5: This WORM chip contains encrypted account information of the owner. Each account listing is encrypted by the bank which holds it by an encryption scheme known only to that bank. Each entry holds the bank's name, the account number, and the bank's LTG number. No other information (current balance or account history, for example) is held in this chip.
Balance: This is a RAM chip which holds the transitory information about accounts, including current balance and the last twenty transactions (or more if the stick has not been updated). This information is for the owners use only and is not generally considered valid by the CVS; it trusts the bank's information, not the credstick's.
AIM5: This is a standard RAM storage chip, holding 5Mp, which can be used for any data the user desires. Typical uses include holding resume, business card data, phone numbers, personal pictures and so on. In some countries (most notably the Ute Nation) votes for an upcoming election can be stored in this chip, then easily and quickly slotted in a street- corner voting booth.