New standards in data security: 256-bit encryption technology in digital weighing technology

HBM also uses this recognized standard with a key size of 256 bits in the DIS2116 digital weighing electronic. The temptation to manipulate data for financial gain is especially great in weighing systems. This refers not only to scales in supermarkets.

Truck scales are also regularly verified by the weights and measures officers for good reason. After all, who can really say when purchasing large quantities of sand, rock, or earth whether the weight shown on the scale is the real weight? The same applies in the opposite sense when removing materials, for example construction waste.

Data is transferred from the load cells to the DIS2116 digital weighing electronic in legal-for-trade mode based on AES encryption. Internal storage of weighing data as well as the date and time are also encrypted. This makes it possible to check the authenticity of the determined data at any time, which is hardly possible in an open PC network with extensive branching. Changes made to the scale are also saved and can later be retraced by weights and measures officers. Manipulation thus becomes readily apparent and is therefore excluded.

Installation of digital weighing electronics does not represent a difficulty for system integrators. Only a few software commands are required to integrate the DIS2116 in higher-level systems. Since all data required for legal-for-trade (LFT) applications (for example date, gross, net, tare, manual tare) are saved internally in encrypted format, the post-processing software does not require any special functions in terms of LFT capability. Therefore standard software can be used to edit the data, which offers significant cost advantages.

Of course the performance capability of the scale system must not suffer due to the 256-bit encryption which is taking place in parallel to processing of measured values. Because of this, both the load cells such as the C16i as well as the electronics are fitted with a 32-bit processor. The 32-bit processor is required in any case for AES encryption and also ensures a high performance level for the entire system. But this is far from the only advantage offered by digital technology.

The weighing electronics have an electronic compensation for the off-center load error. To compensate for mechanical off-center load errors, a load is simply placed on each corner. The process takes only a few minutes – a considerable time saving compared to the same process for analog scales, which can last two or three hours.

The advent of digital technology in weighing systems also makes it possible to implement new functionalities:

• Entry point for scale management (facility management for systems)
• Longer service life because maintenance can be planned and performed in time
• Problem-free transmission
• Status message to the control system
• Faster sensor exchange
• Traceability of adjustment/calibration data
• Center-of gravity display

Numerous interfaces complete the line of digital electronics: RS-232 ports for connecting to a PC, higher level system, printer, or second display; PS2 port for connecting to a standard PC keyboard and a USB port to which a printer can also be connected, making it possible to print required data directly with no problem. An optional interface is also set up for a fieldbus module.

An SD card is used as the storage medium. It serves as a legal-for-trade alibi memory for all settings, for example settings of calibration parameters. This flexible storage solution also makes it possible to transfer all scale parameters to a new unit simply by replacing the SD card.

With the use of digital technology and AES with a 256-bit key length in weighing technology, HBM is setting new standards in the field of data security and information management. The numerous other advantages and functionalities offered by digital technology make weighing electronics and load cells a convenient alternative for many applications, especially for scales with heavy industrial usage. New solutions can also be implemented, for example wireless data transmission from the load cell to the scale display, or to provide electrical power to load cells with independent external power sources (solar, battery or fuel cells).

At the beginning of 1997, the US National Institute of Standards and Technology (NIST) announced an open worldwide competition: They were seeking the successor to DES (Data Encryption Standard). With a key length of just 56 bits, it was by then considered unreliable, and increasing the effective key length to 112 bits by applying DES three times reduced speed drastically.

The standard had furthermore long been under criticism due to the involvement of the National Security Agency (NSA) in its development. Especially the design of the so-called "S boxes" gave rise to speculation about possible back doors that may have been introduced by the NSA to be able to read messages encrypted by the process. For example Alan Konheim, who was involved in DES development, claims he sent the S boxes, which erase the relationship between plain text and secret text, to Washington and that they were then heavily modified. But ultimately it was the unreliability of the outdated standard that forced the NIST to post its invitation for submissions to the competition. And it's just as well they did, since DES can be cracked today with a brute-force attack (trying all possibilities) within three hours.

Criteria of AES
NIST set the following criteria that the new standard, the Advanced Encryption Standard (AES), had to meet:
The AES

• had to be a symmetrical algorithm, specifically a block cipher
• had to be able to use keys 128, 192, and 256 bits in length
• should be easy to implement in terms of both hardware and software and should have above average performance capabilities
• should be able to withstand all methods of cryptoanalysis
• should require limited resources and therefore little storage space
• had to be free of patent law claims so that anyone could use it free of charge.

Rijndael algorithm
Of the 15 algorithms that were submitted to NIST by August 1998, five reached the second round: MARS, RC6, Rijndael, Serpent, and Twofish. All five were uncrackable, but only the Rijndael algorithm demonstrated above average performance in terms of both hardware and software and made limited use of resources. Accordingly it was finally declared the winner in October 2000. The name is derived from its Belgian developers: Joan Daemen and Vincent Rijmen.