Method and system for controlling unauthorized access to information distributed to users

• US 5,586,186 A
• Filed: 07/15/1994
• Issued: 12/17/1996
• Est. Priority Date: 07/15/1994
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Ernst, Michael, Yuval, Gideon A.
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/275,500
• Time in Patent Office: 886 Days
• Field of Search: 380/4, 380/30, 380/25
• US Class Current: 380/30
• CPC Class Codes: G06F 21/10 Protecting distributed programs or content, e.g. vending or licensing of copyrighted material protection in video systems or pay television H04N7/16 ; Digital rights management [DRM]
• CPC Class Codes: G06F 2211/007 Encryption, En-/decode, En-/decipher, En-/decypher, Scramble, (De-)compress
• CPC Class Codes: G06F 2221/2107 File encryption
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• CPC Class Codes: H04L 2209/34 Encoding or coding, e.g. Huffman coding or error correction
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 9/302 involving the integer factorization problem, e.g. RSA or quadratic sieve [QS] schemes

Abstract

A system for controlling unauthorized access to information distributed to users and, more particularly, for controlling unauthorized access to software distributed to users is provided. One method utilizing the system of the present invention enables the software to be encrypted using a single encryption key and to be decrypted using a multiplicity of "decryption" keys, each of which is unique to a particular user. The "decryption" keys are the products of numeric representations of identifying information relating to users and unique user keys generated using the numeric representations and a "true" decryption key. Since each user receives a unique user key and both the numeric representation and the user key are generated using the identifying information, if the user reveals the numeric representation and the user key (or the product of the numeric representation and the user key), the numeric representation and the user key can be traced to the user who revealed them. Another method utilizing the system of the present invention introduces randomness or pseudo-randomness into the decryption scheme to provide an additional level of security to the scheme.

Claims

1. A method for controlling unauthorized access to information distributed to users, the method comprising the steps of:

choosing an encryption parameter and generating from it an encryption key using a public key algorithm;

generating a decryption key using the public key algorithm;

encrypting the information using the encryption parameter and the encryption key;

distributing identical copies of the encrypted form of the information to users;

receiving identifying information from a user;

generating a numeric representation of the identifying information;

generating a unique user key using the numeric representation of the identifying information and decryption key information;

providing the user with the unique user key; and

decrypting the encrypted form of the information using the numeric representation of the identifying information, the unique user key, and the encryption parameter.

2. The method of claim 1,

wherein the step of generating an encryption key includes the step of generating the encryption key using an RSA algorithm, wherein the encryption parameter n is the product of any two prime numbers p and q, wherein φ

(n)=(p-1)(q-1) and the encryption key e is relatively prime to φ

(n);

wherein the step of generating a decryption key includes the step of generating the decryption key using the RSA algorithm, wherein the decryption key d=e^-1 (mod φ

(n)); and

wherein the step of encrypting the information includes the step of encrypting the information using the encryption function E(a)=a^e mod n, wherein a is the information to be encrypted.

3. The method of claim 2, wherein the step of generating a unique user key includes the step of generating the unique user key y using the function y=d/x (mod φ

(n)), wherein x is the numeric representation of the identifying information.

4. The method of claim 3, wherein the step of decrypting the encrypted form of the information includes the step of decrypting the encrypted form of the information using the decryption function D(c)=c^xy mod n, wherein c is the encrypted form of the information.

5. The method of claim 1, wherein the decryption key information is the decryption key.

6. The method of claim 1, wherein the decryption key information is information from which the decryption key can be derived.

7. The method of claim 1, wherein the information distributed to users is software.

8. The method of claim 1, wherein the information distributed to users is stored on CD-ROM.

9. The method of claim 1, wherein the step of receiving identifying information includes the step of receiving unique identifying information from the user.

10. The method of claim 1, wherein the step of receiving identifying information includes the step of receiving a name, a credit card number, and an expiration date for a credit card from the user.

11. The method of claim 1, wherein the step of generating a numeric representation of the identifying information includes the step of generating the numeric representation such that the identifying information is uniquely determinable from the numeric representation and the numeric representation is uniquely determinable from the product of the numeric representation and the unique user key.

12. The method of claim 11, wherein the step of generating the numeric representation includes the step of encoding the identifying information using a Godel numbering.

13. The method of claim 12, wherein the step of generating the numeric representation further includes the step of encoding the identifying information using an error-correcting coding.

14. The method of claim 13, wherein the step of generating the numeric representation further includes the step of determining whether the numeric representation generated using the Godel numbering and the error-correcting coding is uniquely determinable from the product of the numeric representation and the unique user key and if not, modifying the identifying information and generating a numeric representation of the modified identifying information using the Godel numbering and the error-correcting coding.

15. The method of claim 14, wherein the steps of modifying the identifying information and generating a numeric representation of the modified identifying information are repeated until the numeric representation is uniquely determinable from the product of the numeric representation and the unique user key.

16. A method for controlling unauthorized access to information stored on a storage medium, the method comprising the steps of:

generating an encryption key using a public key algorithm;

generating a decryption key using the public key algorithm;

encrypting the information using the encryption key;

storing the encrypted form of the information on the storage medium;

receiving identifying information from a user;

generating a numeric representation of the identifying information;

generating a unique user key using the numeric representation of the identifying information and decryption key information;

providing the user with the unique user key; and

decrypting the encrypted form of the information using the numeric representation of the identifying information and the unique user key.

17. A method for controlling unauthorized access to software stored on CD-ROM, the method comprising the steps of:

selecting an encryption key e such that e is relatively prime to φ

(n), wherein n is the product of any two prime numbers p and q and φ

(n)=(p-1) (q-1);

generating a decryption key d such that d=e^-1 (mod φ

(n));

encrypting the software using the encryption function E(a)=a^e mod n, wherein a is the software to be encrypted;

storing the encrypted form of the software on the CD-ROM;

receiving identifying information from a user;

generating a numeric representation of the identifying information by encoding the identifying information using a Godel numbering and an error-correcting coding;

generating a unique user key y using the function y=d/x (mod φ

(n)), wherein x is the numeric representation of the identifying information;

providing the user with the unique user key y; and

decrypting the encrypted form of the software using the decryption function D(c)=c^xy mod n, wherein c is the encrypted form of the software.

18. A method for generating a unique user key that can be used together with a numeric representation of identifying information relating to a user to decrypt information that has been encrypted using a public key algorithm, the method comprising the steps of:

receiving identifying information from a user;

generating a numeric representation of the identifying information; and

generating a unique user key using the numeric representation of the identifying information and decryption key information.

19. A method for decrypting information that has been encrypted using a public key algorithm, the method comprising the steps of:

receiving identifying information from a user;

receiving a unique user key from the user, the unique user key having been generated using a numeric representation of the identifying information and decryption key information;

generating the numeric representation of the identifying information; and

decrypting the encrypted form of the information using the numeric representation of the identifying information and the unique user key.

20. A system for controlling unauthorized access to information distributed to users, the system comprising:

an encryptor for generating an encryption key and a decryption key using a public key algorithm and for encrypting the information using the encryption key;

a user key generator for receiving identifying information from a user, for generating a numeric representation of the identifying information, and for generating a unique user key using the numeric representation of the identifying information and decryption key information; and

a decryptor for decrypting the encrypted form of the information using the numeric representation of the identifying information and the unique user key.

21. A method for controlling unauthorized access to information distributed to users, the method comprising the steps of:

generating two encryption keys using a public key algorithm;

generating two decryption keys using the public key algorithm;

encrypting the information twice using the two encryption keys;

distributing the two encrypted forms of the information to users;

receiving identifying information from a user;

generating two numeric representations of the identifying information;

generating two unique user keys using the two numeric representations of the identifying information, decryption key information, and a random number;

providing the user with the two unique user keys;

decrypting the two encrypted forms of the information using the two numeric representations of the identifying information and the two unique user keys; and

multiplying the results of the two decryptions to recover the information.

22. The method of claim 21,

wherein the step of generating two encryption keys includes the step of generating the two encryption keys using an RSA algorithm, wherein the encryption keys e and e'"'"' are relatively prime to φ

(n), n is the product of any two prime numbers p and q, and φ

(n)=(p-1) (q-1);

wherein the step of generating two decryption keys includes the step of generating the two decryption keys using the RSA algorithm, wherein d=e^-1 (mod φ

(n)) and d'"'"'=e'"'"'^-1 (mod φ

(n)); and

wherein the step of encrypting the information twice includes the step of encrypting the information twice using the encryption functions E(a)=a^e mod n and E'"'"'(a)=a^e'"'"' mod n, wherein a is the information to be encrypted.

23. The method of claim 22, wherein the step of generating two unique user keys includes the steps of:

selecting the random number r, wherein r ε

Z.sub.φ

(n) and Z.sub.φ

(n) is equal to the set of numbers from 0 to (φ

(n)-1); and

generating two unique user keys y and y'"'"' using the functions y=rd/x (mod =(n)) and y'"'"'=(1-r)d'"'"'/x'"'"' (mod φ

(n)), wherein x and x'"'"' are the numeric representations of the identifying information.

24. The method of claim 23, wherein the step of decrypting the two encrypted forms of the information includes the step of decrypting the two encrypted forms of the information using the decryption functions D(c)=c^xy mod n and D'"'"'(c'"'"')=c'"'"'^x'"'"'y'"'"' mod n, wherein c and c'"'"' are the two encrypted forms of the information.

25. The method of claim 21, wherein the decryption key information is the two decryption keys.

26. The method of claim 21, wherein the decryption key information is information from which the two decryption keys can be derived.

27. The method of claim 21, wherein the information distributed to users is software.

28. The method of claim 21, wherein the information distributed to users is stored on CD-ROM.

29. The method of claim 21, wherein the step of receiving identifying information includes the step of receiving unique identifying information from the user.

30. The method of claim 21, wherein the step of receiving identifying information includes the step of receiving a name, a credit card number, and an expiration date for a credit card from the user.

31. The method of claim 21, wherein the step of generating two numeric representations includes the step of generating the two numeric representations such that the identifying information is uniquely determinable from the two numeric representations and the two numeric representations are uniquely determinable from the products of the two numeric representations and the two unique user keys.

32. The method of claim 31, wherein the step of generating the two numeric representations further includes the step of encoding the identifying information twice using a Godel numbering.

33. The method of claim 32, wherein the step of generating the two numeric representations further includes the step of encoding the identifying information twice using an error-correcting coding.

34. The method of claim 33, wherein the step of generating the two numeric representations further includes the step of determining whether the two numeric representations generated using the Godel numbering and the error-correcting coding are uniquely determinable from the products of the two numeric representations and the two unique user keys and if not, modifying the identifying information and generating two numeric representations of the modified identifying information using the Godel numbering and the error-correcting coding.

35. The method of claim 34, wherein the steps of modifying the identifying information and generating two numeric representations of the modified identifying information are repeated until the two numeric representations are uniquely determinable from the products of the two numeric representations and the two unique user keys.

36. A method for controlling unauthorized access to information stored on a storage medium, the method comprising the steps of:

generating two encryption keys using a public key algorithm;

generating two decryption keys using the public key algorithm;

encrypting the information twice using the two encryption keys;

storing the two encrypted forms of the information on the storage medium;

receiving identifying information from a user;

generating two numeric representations of the identifying information;

generating two unique user keys using the two numeric representations of the identifying information, decryption key information, and a random number;

providing the user with the two unique user keys;

decrypting the two encrypted forms of the information using the two numeric representations of the identifying information and the two unique user keys; and

multiplying the results of the two decryptions to recover the information.

37. A method for controlling unauthorized access to software stored on CD-ROM, the method comprising the steps of:

selecting two encryption keys e and e'"'"' such that e and e'"'"' are relatively prime to φ

(n), wherein n is the product of any two prime numbers p and q and φ

(n)=(p-1) (q-1);

generating two decryption keys d and d'"'"' such that d=e^-1 (mod φ

(n)) and d'"'"'=e'"'"'^-1 (mod φ

(n));

encrypting the software twice using the encryption functions E(a)=a^e mod n and E'"'"'(a)=a^e'"'"' mod n, wherein a is the software to be encrypted;

storing the two encrypted forms of the software on the CD-ROM;

receiving identifying information from a user;

generating two numeric representations of the identifying information by modifying the identifying information and encoding the identifying information and the modified identifying information using a Godel numbering and an error-correcting coding;

selecting a random number r, wherein r ε

Z.sub.φ

(n) and Z.sub.φ

(n) is equal to the set of numbers from 0 to (φ

(n)-1);

generating two unique user keys using the functions y=rd/x (mod φ

(n)) and y'"'"'=(1-r)d'"'"'/x'"'"' (mod φ

(n)), wherein x and x'"'"' are the numeric representations of the identifying information and the modified identifying information;

decrypting the two encrypted forms of the software using the decryption functions D(c)=c^d mod n and D'"'"'(c'"'"')=c'"'"'^d'"'"' mod n, wherein c and c'"'"' are the two encrypted forms of the software; and

multiplying the results of the two decryptions to recover the software.

38. A method for decrypting information that has been encrypted using a public key algorithm, the method comprising the steps of:

receiving identifying information from a user;

receiving two unique user keys from the user, the unique user keys having been generated using two numeric representations of the identifying information and decryption key information;

generating the two numeric representations of the identifying information;

decrypting the two encrypted forms of the information using the two numeric representations of the identifying information and the two unique user keys; and

multiplying the results of the two decryptions to recover the information.

39. A system for controlling unauthorized access to information distributed to users, the system comprising:

an encryptor for generating two encryption keys and two decryption keys using a public key algorithm and for encrypting the information twice using the two encryption keys;

a user key generator for receiving identifying information from a user, for generating two numeric representations of the identifying information, and for generating two unique user keys using the two numeric representations of the identifying information, decryption key information, and a random number; and

a decryptor for decrypting the two encrypted forms of the information using the two numeric representations of the identifying information and the two unique user keys and multiplying the results of the two decryptions to recover the information.