RAD
(Rapid Application Development), an approach that attempts to design interactive systems using small teams working on the same application, development and iterative prototyping techniques within a few months.


Rainbow fluorescence
The property of emitting the colors of the rainbow when excited by UV light.


Rainbow thread
A security thread containing fluorescent pigments that shine in the colors of the rainbow when excited by UV light.


RAM
Random access memory is a processor’s working storage, into which data is loaded and altered during a “session.” RAM is “volatile,” meaning the contents will be lost if the power is cut off.


Random numbers
Random numbers ensure the uniqueness and unpredictability of a session and provide the basis for every authentication between the smart card and the terminal. The principle can be easily explained using the example of a “symmetrical" encryption for which the terminal and the card use the same secret key, when they actually belong to the same system: The terminal generates a random number and sends this to the smart card; this “encrypts” the number and sends it back to the Terminal. The Terminal encrypts the same random number and compares the results. If these are identical, then the smart card is authentic. The smart card can also be used to verify the authenticity of the terminal. In practice, these two steps are performed in one step.

Rattle
Characteristic rustling of a banknote caused by the stiffness of the paper.


Recombination
The mechanical reproduction of a holographic image.


Recycling
The combined functions of banknote depositing and withdrawal performed by special self-service machines at banks. The ATM examines the fitness of the notes deposited, sorting them and making them available for immediate withdrawal by the next customer.


Recycling ATM
A self-service machine that accepts the banknotes deposited by a customer, scans the banknotes’ level of fitness for circulation, then sorts them and pays out the fit notes to the next customer making a withdrawal.


Reflection hologram
As with a picture or painting, a reflection hologram can only be viewed with the light source (white light only) in front of the image. (Cf. transmission hologram.)


Reject compartment
Separate stacker on a banknote processing machine used to hold banknotes that were either not recognized or are suspected of being counterfeit.


Reject rate
Banknotes that a currency processing system does not recognize or unsuccessfully transports are sent to the reject compartment. The reject rate is the number of rejected banknotes in proportion to the number of banknotes fed into the machine. See acceptance rate.


Reject reel
The reject reel is used to store banknotes that either cannot be scanned or are suspected of being counterfeit for later manual inspection, sometimes also referred to as “reconciliation” (BPS^® 2000). The reject reel of the BPS^® 3000 also stores the original banding material.

Reset
Reverting a computer (in this context, an IC card) to a clearly defined original state. If the procedure involves switching the power supply voltage off and on again, it is referred to as a “cold reset” or a “power-on reset.” A warm reset is performed by sending a signal across the reset cable to the card, with the power supply remaining unaffected.


Retrace
Determining the origin of a specific banknote deposit. See PIDSY.


Retract compartment
A deposit terminal slot used to hold banknotes that the customer fails to remove (unintentionally) after canceling a transaction.


Retry counter
Counter that records the number of failed attempts and determines whether a particular code can continue to be used. When the retry counter reaches the maximum value, the code is blocked and can no longer be used. The retry counter usually resets to zero after a successful attempt.


Roaming
Roaming enables mobile phone users to make calls with their handsets when outside their wireless provider’s field of coverage, e.g. when out of country. In order to use a cell phone outside one’s country, it is generally necessary to resort to the communication networks and services of the local (foreign) service providers. Billing for the services offered by a foreign network provider and accessed by the wireless customer is performed by one's own, domestic provider, which then settles the account with the respective provider in the foreign country. An additional fee is charged for making use of roaming services. Such charges can drastically increase the cost of roaming, depending on how much it is used. Roaming services cannot be used with prepaid cards.

ROM
“Read only memory” containing the chip’s hardwired operating system as well as the cryptographic algorithms and applications—in short, all the data required for a large number of cards. ROM is type of non-volatile memory primarily used to store programs and static data, since its contents cannot be altered.


ROM mask
An exposure mask used in semiconductor fabrication to produce the ROM. The term is also used in connection with smart card controllers to refer to the data content of the ROM.


Root certification authority
The certification authority (CA) that issues certificates within a certification chain. In order for a certificate user to validate a certification chain, he or she must first know the root certification authority’s public key.


RSA
The designation for an encryption and authentication algorithm taken from the initials of the last names of its developers: Ron Rivest, Adi Shamir, and Leonard Adleman. RSA has long been used for encryption. It is considered proven and secure when keys of appropriate length are used.


RSA algorithm
The most widely known asymmetric encryption and authentication system, named after its inventors Ron Rivest, Adi Shamir, and Leonard Adleman. Its function is based on multiplying two large prime numbers and through additional operations deriving a set of two numbers: a public key and a private key. The authentication process makes use of these two different keys for encryption and decryption. The recipient of a message can use a public key to verify a message and its sender but cannot impersonate the sender. Both keys (public and private) are generated according to a mathematical rule based on the experience that it is far simpler to generate a large number by multiplying two numbers than to determine the prime factors of a given number. Anyone can quickly multiply 7 and 13 to come up with 91. The other way around, however, it is not necessarily as easy to divide 91 into its (prime) factors of 7 and 13. The security of the procedure lies in the size of the numbers, i.e. the length of the keys. Some applications utilize key lengths of 1024 bits.