Disclosed are various examples for securing the transmission of files to and from a client device. In some examples, an initialization token is identified for a file that includes a number of portions. An algorithm is iteratively applied to the initialization token to determine that no repeated output occurs over a number of iterations corresponding to the number of file portions. Initialization data is transmitted from a client device to a management service that manages access to the file. The initialization token is included in the initialization data if no repeated output occurs when the algorithm is iteratively applied over the number of iterations.

Disclosed are various examples for securing the transmission of files to and from a client device. In some examples, an initialization token is identified for a file that includes a number of portions. An algorithm is iteratively applied to the initialization token to determine that no repeated output occurs over a number of iterations corresponding to the number of file portions. Initialization data is transmitted from a client device to a management service that manages access to the file. The initialization token is included in the initialization data if no repeated output occurs when the algorithm is iteratively applied over the number of iterations.

Methods and apparatus to enable a distinction between “new” and “used” digital content and to enable a market in used digital content files between mobile phone terminals and an electronic store, securely, by means of a wireless telephony network and a server complex to handle contents right management, transaction reporting, inventory, content delivery, payment, and billing. A server receives a signal generated by a wireless user device that was sent over a wireless telephony network. The signal indicates an election for returning at least one previously purchased digital content item. The server deletes user rights for the at least one digital content item identified by the received signal and sends information to the user device that generated the signal. Access to the associated digital content item at the user device is removed according to the sent information.

A method and system for group-oriented encryption and decryption that supports the implementation of the designation and revocation functions of decryption users in a large-scale group. During the encryption, the system acquires a corresponding aggregate function according to an encryption mode; acquires any selected subset S and public parameters, and outputs an aggregate value of the subset S; generates a ciphertext of to-be-transmitted information according to the public parameters, a to-be-transmitted message and the aggregate value; acquires the encryption mode and the subset S comprised in the received ciphertext, operates the subset S and an identity of a current decryptor according to the encryption mode, and outputs a new subset S′; acquires an aggregate function corresponding to the encryption mode during the decryption; outputs an aggregate value of the new subset S′; and decrypts the received ciphertext according to the public parameters and the aggregate value, so as to obtain the to-be-transmitted information.

A method and system for group-oriented encryption and decryption that supports the implementation of the designation and revocation functions of decryption users in a large-scale group. During the encryption, the system acquires a corresponding aggregate function according to an encryption mode; acquires any selected subset S and public parameters, and outputs an aggregate value of the subset S; generates a ciphertext of to-be-transmitted information according to the public parameters, a to-be-transmitted message and the aggregate value; acquires the encryption mode and the subset S comprised in the received ciphertext, operates the subset S and an identity of a current decryptor according to the encryption mode, and outputs a new subset S′; acquires an aggregate function corresponding to the encryption mode during the decryption; outputs an aggregate value of the new subset S′; and decrypts the received ciphertext according to the public parameters and the aggregate value, so as to obtain the to-be-transmitted information.

Aspects related to the secure transfer and use of secret material are described. In one embodiment, an encrypted secret key and encrypted revocation data are imported into a trusted execution environment and decrypted with private provider and vendor keys. In this manner, a provider of cryptographic processes is not exposed to the secret key or revocation data of a customer, as the secret key and revocation data are decrypted and stored within the trusted execution environment but not accessed in an unencrypted form. In turn, the provider can receive various instructions to perform cryptographic operations on behalf of the customer. Based on the outcome of a revocation check using the revocation data, the instructions can be performed by the trusted execution environment.

Aspects related to the secure transfer and use of secret material are described. In one embodiment, an encrypted secret key and encrypted revocation data are imported into a trusted execution environment and decrypted with private provider and vendor keys. In this manner, a provider of cryptographic processes is not exposed to the secret key or revocation data of a customer, as the secret key and revocation data are decrypted and stored within the trusted execution environment but not accessed in an unencrypted form. In turn, the provider can receive various instructions to perform cryptographic operations on behalf of the customer. Based on the outcome of a revocation check using the revocation data, the instructions can be performed by the trusted execution environment.

A communication system and a comparison method for securing a communication path for a legitimate user via a terminal apparatus (“TA”). A vehicle-mounted communication device (“VMCD”) transmits a device ID identifying the VMCD to a TA, acquires a terminal ID from the TA, and transmits the device ID and the terminal ID acquired from the TA to a central apparatus. The TA transmits a terminal ID identifying the TA to the VMCD, acquires a device ID from the VMCD, and transmits the terminal ID and the device ID acquired from the VMCD to the central apparatus. The central apparatus receives a device ID and a terminal ID transmitted from the VMCD and a device ID and a terminal ID transmitted from the TA, and compares the device ID and the terminal ID received from the VMCD with the device ID and the terminal ID received from the TA.

A communication system and a comparison method for securing a communication path for a legitimate user via a terminal apparatus (“TA”). A vehicle-mounted communication device (“VMCD”) transmits a device ID identifying the VMCD to a TA, acquires a terminal ID from the TA, and transmits the device ID and the terminal ID acquired from the TA to a central apparatus. The TA transmits a terminal ID identifying the TA to the VMCD, acquires a device ID from the VMCD, and transmits the terminal ID and the device ID acquired from the VMCD to the central apparatus. The central apparatus receives a device ID and a terminal ID transmitted from the VMCD and a device ID and a terminal ID transmitted from the TA, and compares the device ID and the terminal ID received from the VMCD with the device ID and the terminal ID received from the TA.

A method for key rotation includes initiating key rotation for a user account of a multi-factor authentication platform enabling one-time password authentication using a first symmetric cryptographic key; generating, at an authenticating device, a second symmetric cryptographic key; transmitting, at the authenticating device, the second symmetric cryptographic key to the multi-factor authentication platform; configuring the multi-factor authentication platform and the authenticating device to disable authentication that uses the first symmetric cryptographic key; and configuring the multi-factor authentication platform and the authenticating device to enable authentication that uses the second symmetric cryptographic key.