Blind encryption

• US 5,638,445 A
• Filed: 09/19/1995
• Issued: 06/10/1997
• Est. Priority Date: 09/19/1995
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Thomlinson, Matthew W., Spelman, Jeffrey F.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/530,022
• Time in Patent Office: 630 Days
• Field of Search: 380/21, 380/24, 380/25, 380/30
• US Class Current: 705/77
• CPC Class Codes: G06Q 20/085 involving remote charge determination or related payment systems
• CPC Class Codes: G07F 7/1016 Devices or methods for securing the PIN and other transaction-data, e.g. by encryption arrangements for secret communication, see H04L9/00
• CPC Class Codes: H04L 2209/04 Masking or blinding
• 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 method of processing encrypted communications sent by a first party, the method including the steps of: receiving from the first party a message that has a first part, a second part, a third part and a fourth part, wherein the first part includes a first block of information that is encrypted by using a key k1, the second part includes a second block of information that is encrypted by using a key k2, the third part includes a third block of information that is encrypted by using a key R, and the fourth part includes a fourth block of information that is encrypted by using the key R, wherein the third block of information includes k1 and the fourth block of information includes k2; blinding the fourth part; sending the third part and the blinded fourth part to a recryptor; receiving from the recryptor the k1 key re-encrypted by using a first key; and receiving from the recryptor a fifth block of information which is the blinded fourth block of information that has been encrypted by using a second key.

Claims

1. A method of processing encrypted communications sent by a first party, said method comprising:

receiving from the first party a message that has a first part, a second part, a third part and a fourth part, wherein the first part includes a first block of information that is encrypted by using a key k1, the second part includes a second block of information that is encrypted by using a key k2, the third part includes a third block of information that is encrypted by using a key R, and the fourth part includes a fourth block of information that is encrypted by using the key R, wherein the third block of information includes k1 and the fourth block of information includes k2;

blinding the fourth part; and

sending the third part and the blinded fourth part to a recryptor.

2. The method of claim 1 further comprising:

receiving from the recryptor the k1 key re-encrypted by using a first key; and

receiving from the recryptor a fifth block of information which is the blinded fourth block of information that has been encrypted by using a second key.

3. The method of claim 2 wherein the key R is a public key of a public key-private key pair and wherein each of the keys k1 and k2 are shared keys.

4. The method of claim 3 wherein the first key is a first public key having associated therewith a first private key and the second key is a second public key having associated therewith a second private key.

5. The method of claim 4 wherein the keys k1 and k2 are different keys.

6. The method of claim 5 further comprising:

unblinding the fifth block of information;

sending the second part to a third party; and

sending the unblinded fifth block of information to the third party.

7. The method of claim 5 further comprising:

sending the second part to a third party;

sending the blinded fifth block of information to the third party; and

sending a blinding factor to the third party so that the third party can unblind the blinded fifth block of information.

8. The method of claim 5 wherein the step of blinding comprises multiplying the fourth part by a multiplier.

9. The method of claim 8 wherein the multiplier is b^R mod N, wherein R is the recryptor'"'"'s public key, N is a modulus of R, and b is a random number that is less than N.

10. The method of claim 5 wherein the encrypted communications are part of a commercial transaction by the first party with a merchant party and wherein the third block of information includes an identifier of the merchant party.

11. The method of claim 6 wherein the encrypted communications are part of a commercial transaction by the first party with a merchant party and wherein the fourth block of information includes a credit card number of the first party.

12. The method of claim 6 wherein the encrypted communications are part of a commercial transaction by the first party with a merchant party and wherein the second part includes a purchase instruction.

13. The method of claim 5 further comprising:

using said first private key to decrypt the re-encrypted key k1;

using key k1 to decrypt the first part; and

performing subsequent actions responsive to the information that is disclosed through decrypting the first part.

14. The method of claim 5 further comprising sending the first public key and the second public key to the recryptor.

15. A method of processing a communication from a first party, said method comprising:

receiving from the first party a message that includes a first part and a second part, wherein the first part includes a first block of information that is encrypted by using a first key and the second part includes a second block of information that is blinded and encrypted by using the first key;

decrypting the first part of the message to produce a first decrypted message;

encrypting at least a portion of the first decrypted message using a second key to produce a re-encrypted third block of information;

decrypting the second part of the message to produce a decrypted, blinded message;

re-encrypting the decrypted, blinded message using a third key to produce an re-encrypted/blinded message; and

sending the re-encrypted third block of information and the re-encrypted/blinded message to the first party.

16. The method of claim 15 wherein the first key is a first public key having associated therewith a first private key and wherein the step of decrypting the first part of the message is performed by using the first private key.

17. The method of claim 16 wherein the second key is a second public key having associated therewith a second private key and wherein the step of encrypting at least a portion of the first decrypted message is performed by using the second public key.

18. The method of claim 17 wherein the third key is a third public key having associated therewith a third private key and wherein the step of re-encrypting is performed by using the third public key.

19. The method of claim 18 wherein the first block of information includes a first shared key k1 and the second block of information includes a second shared key k2.

20. The method of claim 19 wherein the first block of information also includes the first shared key k1 concatenated with an identifier of a third party.

21. The method of claim 19 wherein the communication involves a commercial transaction and wherein the second block of information includes the second shared key k2 concatenated with a credit card number of a third party.

22. The method of claim 19 further comprising receiving from the first party the second public key and the third public key.

23. An apparatus for processing an encrypted communication sent by a first party, wherein said encrypted communication includes a first part, a second part, a third part and a fourth part, wherein the first part includes a first block of information that is encrypted by using a key k1, the second part includes a second block of information that is encrypted by using a key k2, the third part includes a third block of information that is encrypted by using a key R, and the fourth part includes a fourth block of information that is encrypted by using the key R, wherein the third block of information includes k1 and the fourth block of information includes k2, said apparatus comprising:

means for blinding the fourth part;

means for sending the third part and the blinded fourth part to a recryptor;

means for receiving from the recryptor the k1 key re-encrypted by using a first key and a fifth block of information which is the blinded fourth block of information that has been encrypted by using a second key.

24. The apparatus of claim 23 further comprising:

means for unblinding the fifth block of information;

means for sending the second part to a third party; and

means for sending the unblinded fifth block of information to the third party.

25. The apparatus of claim 24 further comprising:

first means for decrypting the re-encrypted key k1, said first means using said first private key; and

second means for decrypting the first part, said second means using key k1 to perform said decryption.

26. An apparatus for processing a communication from a second party, said communication including a first part and a second part, wherein the first part includes a first block of information that is encrypted by using a first key and the second part includes a second block of information that is blinded and encrypted by using the first key, said apparatus comprising:

means for decrypting the first part of the message to produce a first decrypted message;

means for encrypting at least a portion of the first decrypted message using a second key to produce a re-encrypted third block of information;

means for decrypting the second part of the message to produce a decrypted, blinded message;

means for re-encrypting the decrypted, blinded message using a third key to produce an re-encrypted/blinded message; and

means for sending the re-encrypted third block of information and the re-encrypted/blinded message to the second party.

27. A method of processing encrypted communications sent by a first party, said method comprising:

receiving from the first party a message that has a first part, a second part, a third part and a fourth part, wherein the first part includes a first block of information that is encrypted by using a key k1, the second part includes a second block of information that is encrypted by using a key k2, the third part includes a third block of information that is encrypted by using a key R, and the fourth part includes a fourth block of information that is encrypted by using the key R, wherein the third block of information includes k1 and the fourth block of information includes k2;

blinding the fourth part; and

sending the third part and the blinded fourth part to a recryptor.