Patent ID: 6973444
Filing Date: 2005-12-06
Classification: G06F,G06Q,G07F,H04L

Abstract:
1. A method for a device to interdependently validate a piece of digital content and a corresponding digital license for rendering the digital content, the digital content being encrypted, the encrypted digital content being decryptable according to a decryption key (KD) and being packaged in a digital content package, the digital content package being provided by a content provider having a public key (PU-C) and a private key (PR-C), the digital license being provided by a license provider having a public key (PU-L) and a private key (PR-L), the device having a public key (PU-D) and a private key (PR-D), the digital content package comprising: the encrypted digital content; and the content provider public key (PU-C) encrypted with the decryption key (KD) and signed by the content provider private key (PR-C) (i.e., (KD (PU-C) S (PR-C))); the digital license comprising: the decryption key (KD) encrypted with the device public key (PU-D) (i.e., (PU-D (KD))); a digital signature from the license provider (without any attached certificate) based on (KD (DRL)) and (PU-D (KD)) and encrypted with the license provider private key (i.e., (S (PR-L))); and a certificate containing the license provider public key (PU-L) and signed by the content provider private key (PR-C) (i.e., (CERT (PU-L) S (PR-C))); the method comprising: obtaining (PU-D (KD)) from the license; applying (PR-D) to (PU-D (KD)) to produce (KD); obtaining (KD (PU-C) S (PR-C)) from the digital content package; applying (KD) to (KD (PU-C) S (PR-C)) to produce (PU-C); applying (PU-C) to (S (PR-C)) to validate (KD (PU-C) S (PR-C)), thereby validating the digital content package; obtaining (CERT (PU-L) S (PR-C)) from the license; applying (PU-C) to (CERT (PU-L) S (PR-C)) to validate (CERT (PU-L) S (PR-C)), thereby validating the content provider, and also to obtain (PU-L); obtaining (S (PR-L)) from the license; and applying (PU-L) to (S (PR-L)), thereby validating the license.