DS1961S Reliability Data1/12/2023
Features and Benefits
- 1128 bits of 5V EEPROM memory partitioned into four pages of 256 bits, a 64-bit write-only secret and up to five general purpose read/write registers
- Write access requires knowledge of the secret and the capability of computing and transmitting a 160-bit MAC as authorization
- Secret and data memory can be write-protected (all or page 0 only) or put in EPROM-emulation mode ("write to 0", page 1)
- On-chip 512-bit SHA-1 engine to compute 160-bit MAC and to generate secrets
- Reads and writes over a wide voltage range of 2.8V to 5.25V from -40°C to +85°C
- Communicates to host with a single digital signal at 14.1kb per second using 1-Wire protocol
- On-chip 16-bit CRC generator for safeguarding data transfers
- Overdrive mode boosts communication speed to 125kbps
- Operating temperature range from -40°C to +85°C
- Minimum 10 years of data retention at 85°C
- Unique, factory-lasered and tested 64-bit registration number (8-bit family code + 48-bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike
- Multidrop controller for 1-Wire net
- Digital identification and information by momentary contact
- Chip-based data carrier compactly stores information
- Data can be accessed while affixed to object
- Button shape is self-aligning with cup-shaped probes
- Durable stainless steel case engraved with registration number withstands harsh environments
- Easily affixed with self-stick adhesive backing, latched by its flange, or locked with a ring pressed onto its rim
- Presence detector acknowledges when reader first applies voltage
The DS1961S combines 1024 bits of EEPROM, a 64-bit secret, an 8-byte register/control page with up to five user read/write bytes, a 512-bit SHA-1 engine and a fully featured 1-Wire® interface in a rugged iButton® device. Data is transferred serially via the 1-Wire protocol, which requires only a single data lead and a ground return. The DS1961S has an additional memory area called the scratchpad that acts as a buffer when writing to the main memory, the register page or when installing a new secret. Data is first written to the scratchpad from where it can be read back. After the data has been verified, a copy scratchpad command will transfer the data to its final memory location, provided that the DS1961S receives a matching 160-Bit message authentication code (MAC). The computation of the MAC involves the secret and additional data stored in the DS1961S including the device's Identity Register. Only a new secret can be loaded without providing a MAC. The SHA-1 engine can also be activated to compute 160-bit MAC when reading a memory page or to compute a new secret, instead of loading it.
The DS1961S understands a unique command "Refresh Scratchpad." Proper use of a refresh sequence (see Writing with Verification section) after a copy scratchpad operation reduces the number of weak bit failures in a touch environment. The refresh sequence also provides a means to restore functionality in a device with bits in a weak state.
Each DS1961S has its own 64-bit ROM registration number that is factory lasered into the chip to provide a guaranteed unique identity for absolute traceability. The durable stainless steel package is highly resistant to environmental hazards such as dirt, moisture, and shock. Its compact coin-shaped profile is self-aligning with mating receptacles, allowing the DS1961S to be easily used by human operators. Accessories permit the DS1961S to be mounted on almost any surface including plastic key fobs and photo-ID badges.
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
The eCash Evaluation Kit demonstrates the speed, reliability, and security of a SHA-1 based iButton® eCash system. The provided eCash debit board is a complete stand-alone module that will perform monetary debits in a fast 100ms. The eCash debit board has a serial interface that allows a PC or microprocessor to monitor or provide manual control of the debit process. Utilizing the serial interface, this demo could easily be integrated into a real eCash or access control system.
Web-Based Kit Description and Instructions are also available.
Features & Benefits
- Stand-alone eCash evaluation circuit board with LCD display and Audible feedback.
- Supports both DS1963S and DS1961S iButton SHA-1 devices as debit tokens.
- Once initialized, the DS1963S coprocessor on the debit board keeps the money secret secure
- Secure eCash debits in 100ms (approximate).
- 2 Java™ programs (compatible with Windows® and Linux) provided for download to initialize eCash coprocessors and tokens as well as to monitor evaluation board.
- Evaluation board can be used as a component in a larger control system (Service Control Unit).
- Complete firmware source provided in portable 'C' code.
- Schematic design and list of components of eval board provided.
- Evaluation board can be used for eCash code development with the onboard single-cycle 8051 compatible DS89C420.
Documentation & Resources
iButton Data Loggers5/17/2019
Secure Access Control Through Challenge and Response Authentication4/1/2011
How to Power the Extended Features of 1-Wire® Devices6/17/2008
Software Methods to Achieve Robust 1-Wire® Communication in iButton® Applications9/11/2007
What Is an iButton Device?5/17/2006
Protect Your R&D Investment with Secure Authentication12/22/2005
White Paper 9: Are SHA-1 Devices Still Secure Enough?5/19/2005
White Paper 1: SHA Devices Used in Small Cash Systems12/20/2002
Securing Electronic Transactions Using SHA-1 Secure Hash Algorithm10/21/2002
White Paper 8: 1-Wire® SHA-1 Overview9/10/2002
White Paper 3: Why are 1-Wire SHA-1 Devices Secure?6/7/2002
Challenge and Response with 1-Wire® SHA Devices3/12/2002
Maxim Digital Monetary Certificates3/8/2002
Passwords in SHA Authentication2/22/2002
DS1961S Companion Parts
Recommended Related Parts
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