| 摘要 |
Digital content is rendered on a device by transferring the content to the device and obtaining a digital license corresponding to the content. A sub-license corresponding to and based on the obtained license is composed and transferred to the device, and the content is rendered on the device only in accordance with the terms of the sub-license. The content is encrypted and decryptable according to a content key, and the sub-license includes the content key encrypted and decryptable according to a secret. The sub-license also includes indexing information identifying the secret to the device. The indexing information in the sub-license is obtained to identify the secret, and the secret is acquired based at least in part on the indexing information. The secret is then applied to the encrypted content key to decrypt and obtain the content key, and the obtained content key is applied to the encrypted content to decrypt and obtain the content. To compose the sub-license and also to render the content, the secret is derived by obtaining a device identifier, acquiring a super-secret, and applying the obtained device identifier and super-secret to a function to derive the secret.
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