Differential power analysis method and apparatus

• US 7,587,044 B2
• Filed: 12/03/2001
• Issued: 09/08/2009
• Est. Priority Date: 01/02/1998
• Status: Expired due to Fees

• Current Assignee: Cryptography Research, Inc. (Rambus Inc.)
• Original Assignee: Cryptography Research, Inc. (Rambus Inc.)
• Inventors: Jun, Benjamin C., Kocher, Paul C., Jaffe, Joshua M.
• Primary Examiner(s): Barron, Jr.; Gilberto
• Assistant Examiner(s): Nobahar; Abdulhakim
• Application Number:
  US10/005,105
• Publication Number:
  US 20020124178A1
• Time in Patent Office: 2,836 Days
• Field of Search: 380/1, 380/37, 380/204, 380/207, 380/218, 380/252, 380/253, 380/254, 713/159, 713/172, 713/185, 713/194, 713/340, 726/9, 726/20, 726/25, 705/41, 705/65, 705/66
• US Class Current: 380/1
• CPC Class Codes: G06F 1/06 Clock generators producing several clock signals G06F1/08 - G06F1/14 take precedence
• CPC Class Codes: G06F 1/266 Arrangements to supply power to external peripherals either directly from the computer or under computer control, e.g. supply of power through the communication port, computer controlled power-strips
• CPC Class Codes: G06F 1/3225 of memory devices
• CPC Class Codes: G06F 21/755 with measures against power attack
• CPC Class Codes: G06F 21/77 in smart cards
• CPC Class Codes: G06F 2207/7223 Randomisation as countermeasure against side channel attacks
• CPC Class Codes: G06F 2207/7266 Hardware adaptation, e.g. dual rail logic; calculate add and double simultaneously
• CPC Class Codes: G06F 7/00 Methods or arrangements for processing data by operating upon the order or content of the data handled logic circuits H03K19/00
• CPC Class Codes: G06K 19/073 Special arrangements for circuits, e.g. for protecting identification code in memory protection against unauthorised use of computer memory G06F12/14
• CPC Class Codes: G06K 19/07363 by preventing analysis of the circuit, e.g. dynamic or static power analysis or current analysis
• CPC Class Codes: G06Q 20/341 Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• CPC Class Codes: G06Q 20/382 insuring higher security of transaction
• CPC Class Codes: G06Q 20/409 Device specific authentication in transaction processing
• CPC Class Codes: G07F 7/08 by coded identity card or credit card or other personal identification means without personal verification means G07F7/02
• CPC Class Codes: G07F 7/082 Features insuring the integrity of the data on or in the card
• CPC Class Codes: G07F 7/1008 Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system
• CPC Class Codes: G09C 1/00 Apparatus or methods whereby a given sequence of signs, e.g. an intelligible text, is transformed into an unintelligible sequence of signs by transposing the signs or groups of signs or by replacing them by others according to a predetermined system cryptographic typewriters G09C3/00
• CPC Class Codes: H04L 2209/04 Masking or blinding
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/805 : Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 9/003 : for power analysis, e.g. differential power analysis [DPA] or simple power analysis [SPA]
• CPC Class Codes: H04L 9/0618 : Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation

Abstract

Information leaked from smart cards and other tamper resistant cryptographic devices can be statistically analyzed to determine keys or other secret data. A data collection and analysis system is configured with an analog-to-digital converter connected to measure the device'"'"'s consumption of electrical power, or some other property of the target device, that varies during the device'"'"'s processing. As the target device performs cryptographic operations, data from the A/D converter are recorded for each cryptographic operation. The stored data are then processed using statistical analysis, yielding the entire key, or partial information about the key that can be used to accelerate a brute force search or other attack.

Claims

1. A method for evaluating the security of a cryptographic device to recover useful information about a key, said device containing at least said key and a circuit configured to perform cryptographic operations using said key, said method comprising:

(a) connecting said device to an analog-to-digital converter configured to measure an attribute related to operation of said device;

(b) sending a plurality of command sequences to said device, where each said command sequence causes said device to perform a cryptographic operation to process data using said key;

(c) during processing of each said cryptographic operation, recording a plurality of measurements of said attribute by using said analog-to-digital converter; and

(d) determining whether information about said key is leaking from said device by statistically combining said recorded measurements.

2. The method of claim 1 further comprising temporally aligning data points corresponding to a point of interest within said plurality of measurements.

3. A method for evaluating the security of a cryptographic device to recover useful information about a key, said device containing at least said key and a circuit configured to perform cryptographic operations using said key, said method comprising:

(a) connecting said device to an analog-to-digital converter configured to measure electromagnetic radiation during operation of said device;

(b) sending a plurality of command sequences to said device, where each said command sequence causes said device to perform a cryptographic operation to process data using said key;

(c) during processing of each said cryptographic operation, recording a plurality of measurements of said radiation by using said analog-to-digital converter; and

(d) determining whether information about said key is leaking from said device by statistically combining said recorded measurements.

4. The method of claim 3 where said step (d) further includes determining information about said key.

5. The method of claim 4 where said information about said key is usable to reduce an amount of effort required for a brute force attack against said key.

6. The method of claim 5 where said information about said key includes values of a plurality of key bits.

7. A method for evaluating the security of a cryptographic device to recover useful information about a key, said device containing at least said key and a circuit configured to perform cryptographic operations using said key, said method comprising:

(a) connecting said device to an analog-to-digital converter configured to measure an amount of power consumed on an external power input to said device;

(b) sending a plurality of command sequences to said device, where each said command sequence causes said device to perform a cryptographic operation to process data using said key;

(c) during processing of each said cryptographic operation, recording a plurality of measurements of said power by using said analog-to-digital converter; and

(d) determining whether information about said key is leaking from said device by statistically combining said recorded measurements.

8. The method of claim 7 where said cryptographic operation includes transforming with a block cipher.

9. The method of claim 8 where said block cipher includes DES.

10. The method of claim 9 where said data includes an input to said DES block cipher operation.

11. The method of claim 9 where said data includes an output from said DES block cipher operation.

12. A system for evaluating the security of a cryptographic hardware, comprising:

(a) a device containing at least a key and a circuit configured to perform cryptographic operations using said key;

(b) an analog-to-digital converter connected to said device and configured to measure an attribute related to operation of said device;

(c) data storage system configured to record a plurality of measurements of said attribute, where said measurements are taken by said analog-to-digital converter during processing of each said cryptographic operation; and

(d) statistical processing system for combining said measurements to determine whether information about said key is leaking from said device.

13. The system of claim 12 where said attribute includes electromagnetic radiation from said device.

14. The system of claim 12 where said attribute includes variations in an amount of power consumed on an external power input to said device.

15. The system of claim 14 where said cryptographic operation includes transforming using a block cipher.

16. The system of claim 13 where said element (d) is configured to determine information about said key.

17. The system of claim 12 further comprising a data filtering system configured to temporally align data points corresponding to a point of interest within said plurality of measurements.

18. A method for analyzing externally measurable characteristics of a cryptographic device, said device containing a secret key and configured to perform cryptographic operations with said key, to recover information about said key, said method comprising:

(a) connecting said device to an analog-to-digital converter configured to measure said characteristic during operation of said device;

(b) during a said cryptographic operation, using said analog-to-digital converter to measure a plurality of measurements of said attribute;

(c) storing said set of measurements in a memory;

(d) repeating said (b) and (c) a plurality of times to produce a plurality of sets;

(e) computing the alignment of said measurements in said plurality of sets such that measurements corresponding to a single point of interest can be compared;

(f) generating a guess of a value of a portion of said key;

(g) using said guess, computing an average of a subset of said aligned measurements; and

(h) verifying correctness of said guess by detecting existence of a bias in said average.

19. The method of claim 18 where said characteristic is an amount of power consumed on an external power input to said device.