Abstract: Some embodiments provide a method for performing a cryptographic process. The method receives first and second cipher keys. The method generates a set of subkeys corresponding to each of the first and second cipher keys. The set of subkeys for the first cipher key is dependent on the first cipher key and the second cipher key. The method performs the cryptographic process by using the generated sets of subkeys.

Abstract: Methods, media, and systems for, in one embodiment, protecting one or more keys in an encryption and/or decryption process can use precomputed values in the process such that at least a portion of the one or more keys is not used or exposed in the process. In one example of a method, internal states of an AES encryption process are saved for use in a counter mode stream cipher operation in which the key used in the AES encryption process is not exposed or used.

Abstract: Some embodiments provide a method for performing an iterative block cipher. Line rotations and column rotations are combined to have a diversity of representations of the AES state. These protections can be performed either in static mode where the rotations are directly included in the code and the tables or in dynamic mode where the rotations are chosen randomly at execution time, depending on some entropic context variables. The two modes can also be advantageously combined together.

Abstract: The fake cryptographic layer obfuscation technique can be used to lure an attacker into expending reverse engineering efforts on sections of code the attacker would normally ignore. To do this the obfuscation technique can identify sections of code that are likely to be of lesser interest to the attacker and disguise them as higher value sections. This can be achieved by transforming a lower value section of code to include code patterns, constants, or other characteristics known to exist in sections of code of higher value, such as cryptographic routines. To transform a code section, the obfuscation technique can use one or more program modifications including control flow modifications, constant value adjustments to simulate well-known cryptographic scalars, buffer extensions, fake characteristic table insertion, debug-like information insertion, derivation function-code generation linking, and/or cryptographic algorithm specific instruction insertion.

Abstract: A software version control system manages versioned applications in a client-server computing system environment. Thereby this is a management system for computer application (software) distribution where a number of client devices coupled to a server may be executing different versions of a particular computing application. The system manages updates to the applications and enforces rules or policies to use the most recent version whenever possible.

Abstract: Some embodiments provide for an improved method for performing AES cryptographic operations. The method applies a look up table operation that includes several operations embedded within look up tables. The embedded operations include a permutation operation to permute several bytes of AES state, a multiplication operation to apply a next round's protection to the AES state, an affine function and an inverse affine function to conceal the multiplication operation, and an inverse permutation operation to remove a previous round's protection. Some embodiments provide for an optimized method for efficiently performing such protected AES operations. The method alternates rounds of AES processing between software processing (e.g. processing by a CPU, performed according to software instructions) and hardware processing (e.g. processing by cryptographic ASIC).

Abstract: An authentication challenge system for performing secondary authentication for an account associated with an online store is described. In one embodiment, the authentication challenge system includes a question generation engine, which can derive a series of questions based upon activity associated with a user account of an online store; a network interface, which can transport the series of one or more questions derived by the question generation engine to authenticate the user to the online store; a confidence engine, which can determine a required confidence level for a successful authentication, and can compute a confidence score of the user identity; and a quality engine, which can adjust the question generation engine and the confidence engine based upon an analysis of question and answer metrics across multiple accounts of the online store. The online store can include digital media, such as music, movies, books or applications for electronic computing devices.

Abstract: The embodiments set forth systems and techniques to activate and provide other device services for user devices. An activation manager is configured to activate a user device by receiving an activation request for the device, accepting previously stored and encrypted trusted data for the device, getting current data for the device, determining whether the current data compares with the trusted data, and sending an authorization to activate the device when the current data compares favorably with the trusted data. Data can include a seed component divided into seed segments that are each combined with a unique device identifier using varying cryptographic primitives. Each encrypted seed segment and unique device identifier combination can be dedicated to a different device use or service, and can be used separately for device identification for that use or service.

Abstract: This application relates to embodiments for providing a content stream to a device from a content server based on a protocol that is established between the device and an account server. The account server can initiate a session with the device and provide the device with a list of channels available for a user account associated with the device. When a channel is selected at the device, conditional access information can be provided from the account server to the device, which can thereafter relay the conditional access information to the content server. The content server can use the conditional access information to verify that the device has the appropriate permission to receive streaming content. In this way, because the conditional access information originates at the account server, permission to access streaming content can be managed by correspondence between the account server and the device, rather than the content server.

Abstract: Some embodiments provide a method for performing an iterative block cipher. Line rotations and column rotations are combined to have a diversity of representations of the AES state. These protections can be performed either in static mode where the rotations are directly included in the code and the tables or in dynamic mode where the rotations are chosen randomly at execution time, depending on some entropic context variables. The two modes can also be advantageously combined together.

Abstract: Some embodiments provide a method for performing a block cryptographic operation that includes a plurality of rounds. The method receives a message that includes several blocks. The method selects a set of the blocks. The set has a particular number of blocks. The method applies a cryptographic operation to the selected set of blocks. A particular round of the cryptographic operation for a first block in the set is performed after a later round than the particular round for a second block in the set, while a different particular round for the first block is performed before an earlier round than the different particular round for the second block. In some embodiments, at least two rounds for the first block are performed one after the other without any intervening rounds for any other blocks in the set.

Abstract: A video on demand system in the context of the Internet, for video rentals. A user accesses an on-line store to rent a video program or movie. The rental is for a limited time (such as 30 days) and within that thirty days, the video program or movie can only be viewed for a 24 hour time window. The time limits are enforced by the on-line store which maintains a database of each rental transaction and allows supply of the needed keys for decrypting the (encrypted) video or movie only if within the time limits.

Abstract: Some embodiments provide a method for performing a cryptographic process. The method receives first and second cipher keys. The method generates a set of subkeys corresponding to each of the first and second cipher keys. The set of subkeys for the first cipher key is dependent on the first cipher key and the second cipher key. The method performs the cryptographic process by using the generated sets of subkeys.

Abstract: Methods, media and systems that use an encoded opaque pointer in an API between a client process and a library process. An encoded opaque pointer, in one embodiment, can be received by the library process from the client process, and the library process can decode the opaque pointer to obtain an address in memory containing a data structure pointed to by the opaque pointer. The library process can operate on the data structure to create a revised or processed data structure, stored in the same or different address in heap memory or stack memory, and the library process can encode and return a new opaque pointer, for the processed data structure, to the client process.

Abstract: Methods, media, and systems for, in one embodiment, protecting one or more keys in an encryption and/or decryption process can use precomputed values in the process such that at least a portion of the one or more keys is not used or exposed in the process. In one example of a method, internal states of an AES encryption process are saved for use in a counter mode stream cipher operation in which the key used in the AES encryption process is not exposed or used.

Abstract: Some embodiments of the invention provide a content-distribution system for distributing content under a variety of different basis. For instance, in some embodiments, the content-distribution system distributes device-restricted content and device-unrestricted content. Device-restricted content is content that can only be played on devices that the system associates with the particular user. Device-unrestricted content is content that can be played on any device without any restrictions. However, for at least one operation or service other than playback, device-unrestricted content has to be authenticated before this operation or service can be performed on the content. In some embodiments, the system facilitates this authentication by specifying a verification parameter for a piece of device-unrestricted content.

Abstract: A video on demand system in the context of the Internet, for video rentals. A user accesses an on-line store to rent a video program or movie. The rental is for a limited time (such as 30 days) and within that thirty days, the video program or movie can only be viewed for a 24 hour time window. The time limits are enforced by the on-line store which maintains a database of each rental transaction and allows supply of the needed keys for decrypting the (encrypted) video or movie only if within the time limits.

Abstract: The disclosed hash and message padding functions are based on the permutation composition problem. To compute a hash of a message using permutation composition based hashing, the message is split into equal size blocks. For each block, a permutation composition value is computed. The block permutation composition values are then combined through composition to generate an overall permutation composition value. The hash of the message is then based on the overall permutation composition value. To pad a message using permutation composition based padding, the message is split into equal size blocks. For each block, a permutation composition value is computed and the permutation composition value is added to the block. The padded blocks are then recombined to generate the padded message.

Abstract: Some embodiments of the invention provide a content-distribution system. In some embodiments, the content-distribution system distributes device-restricted content and device-unrestricted content. Device-restricted content is content that can only be played on devices that the system associates with the particular user. Device-unrestricted content is content that can be played on any device without any restrictions. However, for at least one operation or service other than playback, device-unrestricted content has to be authenticated before this operation or service can be performed on the content. In some embodiments, the system facilitates this authentication by specifying a verification parameter for a piece of device-unrestricted content.

Abstract: Some embodiments provide a method for performing a block cryptographic operation that includes a plurality of rounds. The method receives a message that includes several blocks. The method selects a set of the blocks. The set has a particular number of blocks. The method applies a cryptographic operation to the selected set of blocks. A particular round of the cryptographic operation for a first block in the set is performed after a later round than the particular round for a second block in the set, while a different particular round for the first block is performed before an earlier round than the different particular round for the second block. In some embodiments, at least two rounds for the first block are performed one after the other without any intervening rounds for any other blocks in the set.