Patent ID: 7796751
Filing Date: 2010-09-14
Classification: H04L

Abstract:
1. A method for operating an encryption system which provides for operations (a) through (m) defined below, the method being for generating a recipient decryption key RDEC for a recipient z in the encryption system to enable the recipient to decrypt encrypted digital messages from a message sender, wherein the recipient z is n+1 levels below a root authorizer Au 0 in a hierarchy, and wherein the recipient is associated with a recipient ID-tuple (ID z1 , . . . , ID z(n+1) ) that includes identity information ID z(n+1) associated with the recipient and identity information ID zi associated with each of n lower-level authorizers Au 1 , . . . Au n in the hierarchy between the root authorizer and the recipient, wherein n≧1, the method comprising performing, by one or more machines each of which comprises one or more processors, at least one of operations (Au 0 ), (Au 1 ), . . . (Au n ) each of which is performed by one or more of the one or more machines each of which comprises one or more processors, wherein: the operation (Au the operations (a) through (m) are as follows: (a) generating a first cyclic group (b) selecting a non-degenerate bilinear pairing a capable of generating an element of the second cyclic group (c) selecting a root generator P (d) selecting a random root key generation secret s (e) generating a root key generation parameter Q (f) selecting a first function H (g) selecting a second function H (h) generating an element P (i) for each i such that 1≦i≦n, in the operation (Au (j) for each i such that 1≦i≦n, in the operation (Au (k) for each i such that 1≦i≦n, in the operation (Au (l) generating a recipient element P (m) in the operation (Au associated with the recipient, wherein: a key formed from a recipient encryption key RENC and a key formed from the recipient decryption key RDEC are a public key/private key pair the recipient encryption key RENC is generated using identity information of at least one of the authorizers; each said encrypted digital message is encrypted using a recipient public key RPUB and a recipient encryption key RENC, and is decryptable by the recipient using a recipient private key RPRIV and the recipient decryption key RDEC; the recipient public key RPUB and the recipient private key RPRIV form a public key/private key pair