Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
  • H04L9/30—Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
  • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
  • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
  • H04L9/0838—Key agreement, i.e. key establishment technique in which a shared key is derived by parties as a function of information contributed by, or associated with, each of these
  • H04L9/0841—Key agreement, i.e. key establishment technique in which a shared key is derived by parties as a function of information contributed by, or associated with, each of these involving Diffie-Hellman or related key agreement protocols
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
  • H04L9/30—Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy
  • H04L9/3066—Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy involving algebraic varieties, e.g. elliptic or hyper-elliptic curves
  • H04L9/3073—Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy involving algebraic varieties, e.g. elliptic or hyper-elliptic curves involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing

Definitions

• the invention relates to a method for generating a common secret data item between a first user facility and a second user facility through by each such user facility executing mutually symmetric operations on respective complementary data that are based on respectively unique quantities that are at least in part secret, and wherein an outcome of said operations is used in both said user facilities as said common secret data item as has been furthermore recited in the preamble of Claim 1.
• Shared key generation is an important issue in cryptography. The issue has spread to application fields such as Pay TV Systems in consumer electronics and various identification procedures.
• the secret data item may be used as an encryption or decryption key, for effecting mutual authentication among the user facilities, or other.
• Prior art has widely considered Diffie-Hellmann schemes, but these schemes disadvantageously lack a control mechanism for checking the authenticity of the calculated secret data item.
• a certificate based system allows to set up the shared secret data item has been proposed in US Patent 5,218,637, attorney docket PHQ 90.021 assigned to the present assignee, and among others by one of the coinventors of the present invention.
• This art solves the problem, but on the other hand requires a complex organization utilizing at least two levels of public key cryptography.
• a first object of the present invention is to use only a single integrated cryptography level. This implies that no second secret data item will be required to effect a verification operation.
• a further object of the present invention is to allow a compact representation of the various quantities and data items used.
• a first embodiment of the present invention bases on the usage of the so-called Weil Pairings that have been amply discussed in the explicit paper presented on CRYPTO 2001 by Dan Boneh & Matt Franklin, entitled "Identity Based Encryption from the Weil Pairing".
• a second and even broader embodiment of the present invention bases on het usage of the so-called Abelian Varieties, and of which elliptic curves on which the Weil Pairings are effected constitute a sub-class. None of the above concepts have however been considered for the same manner of operating and objects as the present invention. Abelian varieties have been amply discussed in the explicit paper presented on CRYPTO 2002 by K. Rubin & A. Silverberg, entitled “Supersingular Abelian Varieties in Cryptology". A further advantageous aspect of the present invention is that it will allow compact representations due to the straightforward mathematical procedures effectively used.
• the invention also relates to a system comprising a first user facility and a second user facility, and being arranged to communicate according to the method as claimed in Claim 1, to a device being arranged to operate as the first and/or second user facility in a system as claimed in Claim 3, and to a computer program product comprising computer instructions for controlling one or more data processing oriented hardware entities to implement a method as claimed in Claim 1. Further advantageous aspects of the invention are recited in dependent Claims.
• Figure 1 a system comprising various devices that are interconnected via a network and are arranged to operate in accordance with the invention
• Figure 2 a generalization of the system of Figure 1.
• a basic embodiment of the present invention bases on the Weil pairing, which is a bilinear mapping from elliptic curves to finite fields. It is used to express the Discrete Log problem on finite fields in terms of compact representations on an elliptic curve.
• This procedure allows to use a shared secret data item and further parameters that can have bit lengths less than 200 bits, whilst still presenting codebreakers with computational complexities that compare with, or are larger than those of prior art systems to render such codebreaking effectively unfeasible.
• the proposed system is furthermore very robust in that knowledge of the data of a finite number of participants will not give away the system secret which otherwise would have allowed the generation of new shared keys with arbitrary compliant users.
• every user or device has its own unique parameters, which allows to set up a revocation scheme on top of the standard scheme for excluding selected devices when such becomes necessary.
• the system allows the generating of shared secret data items between any pair of users whilst requiring much less storage capacity than classical systems.
• the proposed protocol of the present embodiment bases on an extended version of the Diffie-Hellmann problem.
• the Computational Diffie-Hellmann (CDH) problem looks as follows. Given a point P € E and given aP and bP, there exists no algorithm that computes abP in polynomial time.
• the present invention applies an extended Diffie-Hellmann problem or EDH which regarding the present invention is defined as follows:
• Each of two user facilities gets the following secret data items from a trusted third party, which items hereinafter being listed for user i (note that the trusted party may be one of the two cooperating user facilities):
• the protocol can be made more efficient by already computing the evaluation of the Weil Pairing e((t ⁇ + r ⁇ t ⁇ 2 )P, D(P))in advance. This will avoid the necessity to do the computation of this Weil Pairing at the execution of the protocol proper, although at a trading-off price of a raised storage requirement.
• Figure 1 illustrates a system 100 comprising various devices 101-105 that are interconnected via a network and are arranged to operate in accordance with the invention.
• the system is an in-home system, that may comprise devices such as a radio receiver, a television set, etcetera.
• a particular device is the system master, and will control the others.
• Content is generally received through one or more of the devices, such as a residential gateway or settop box 101, from an external source, such as broadband, Internet or satellite.
• the content is transferred over the network for appropriate rendering in one of the devices.
• all devices in the in-home network will implement the security framework in accordance with the implementation requirements.
• these devices can authenticate each other and distribute content in a secure manner. Access to the content proper will be managed by the security system. This will prevent against unprotected content leaking away to unauthorized devices and also, against data originating from untrusted devices entering into the system. With such protection, devices may only distribute content to other devices which they have successivefully authenticated beforehand. This ensures that an adversary may not receive unauthorized copies through a malicious device.
• a particular device will only be able to successivefully authenticate itself if it was built by an authorized manufacturer, for example because only authorized manufacturers will know a particular secret that is necessary for successiveful authentication, because their devices are provided with a certificate issued by a Trusted Third Party.
• FIG 2 illustrates a generalization of the system of Figure 1.
• a Prover P a Verifier V
• a trusted third party TTP cooperate.
• the Verifier V should want to authenticate the prover P through using information received from the Trusted Tird Party TTP.
• the authentication should be mutual, so that also the Prover P would know that the Verifier V were authentic.
• the information necessary to authenticate the Verifier V to the Prover P is assumed to have been distributed beforehand from the TTP to the parties P and V. This can be done over a suitable communication facility between the three parties. This renders the protocol dynamic and allows updating of the information in case an adversary would manage to obtain unauthorized access to a secret distributed previously.
• the prover P and verifier V can be devices such as carrier 120 in Figure 1, that is equipped with a chip that provides the necessary functionality, and furthermore the audio playback device 105. In such case, there will most likely be no communication channel from the TTP to Prover P and Verifier V. Distribution of the secrets must then be effected beforehand, such as during manufacturing.
• the prover comprises a networking module 301, a cryptographic processor 302, and a storage medium 303. Using the networking module 301, Prover P can transmit and receive data with respect to the Verifier V.
• the networking module 301 could be connected to the network 110 in Figure 1, or rather establish a direct connection such as wireless with the verifier V.
• the cryptographic processor 302 is arranged to execute the method according to the present invention.
• this processor 302 will be realized as a combination of hardware and software, but alternatively it could be realized entirely in either one of these, such as by a collection of software modules or objects.
• the Prover P may store in the storage medium various parameters of the algorithm to execute, but it may furthermore also hold some content to distribute to the Verifier V after successive authentication.
• the storage medium 303 may furthermore be used to store the information received from the TTP. To enhance the security of the system, rather than storing the individual parameter data, one or more intermediate calculation results could be stored instead or additionally.
• the Verifier V comprises a networking module 311, a cryptographic processor 312, and a storage facility 313 with the functionality thereof corresponding to that of the Prover P. If the Verifier V is embodied as a carrier with a Chip-in-Disc, then the storage facility 313 may correspond to the storage available to any optical or other disc, but will preferably be stored in ROM of the Chip-in-Disc.
• the Prover P and the Verifier V may be provided with a pseudorandom number generator 304, 314 that is realized in hardware or software, and provides cryptographically strong pseudo-random numbers. These numbers are used in various preferred applications of the present invention.
• T y t y * P, and the numerals indicating the correspondence with the earlier representation.

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• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Theoretical Computer Science (AREA)
• Computing Systems (AREA)
• General Physics & Mathematics (AREA)
• Mathematical Analysis (AREA)
• Mathematical Optimization (AREA)
• Mathematical Physics (AREA)
• Pure & Applied Mathematics (AREA)
• Algebra (AREA)
• Physics & Mathematics (AREA)
• Storage Device Security (AREA)

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• 2003
  • 2003-08-11 KR KR1020057004732A patent/KR20050057474A/ko not_active Withdrawn
  • 2003-08-11 AU AU2003255923A patent/AU2003255923A1/en not_active Abandoned
  • 2003-08-11 JP JP2004537385A patent/JP2006500814A/ja not_active Withdrawn
  • 2003-08-11 US US10/528,487 patent/US20060050886A1/en not_active Abandoned
  • 2003-08-11 WO PCT/IB2003/003641 patent/WO2004028075A1/en not_active Ceased
  • 2003-08-11 EP EP03797422A patent/EP1543649A1/en not_active Withdrawn
  • 2003-08-11 CN CNA038221918A patent/CN1682485A/zh active Pending

Non-Patent Citations (3)

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