摘要:
A flexible framework for generating “scalable layered access” codestreams allows a bitstream architect to select the number of access types and the number of access layers within each access type. At least some of the access layers are encrypted (or scrambled). Some of the access layers may be left unencrypted or unscrambled to allow free access to those layers. The framework facilitates simultaneous access of multimedia content by different users enjoying selective decryption of different access types and different access layers. An exemplary key schema for the framework sends only one or only a few keys to an end user for a given access layer, from which decryption keys for the content can be derived by hashing and then combining under a Group Diffie-Hellman key agreement. In one implementation, only one key is sent in a license to an end user and other partial key information for Group Diffie-Hellman combination with the licensed key is included in the publicly distributed codestream.
摘要:
Systems and methods configured for recoding an odd integer and elliptic curve point multiplication are disclosed, having general utility and also specific application to elliptic curve point multiplication and cryptosystems. In one implementation, the recoding is performed by converting an odd integer k into a binary representation. The binary representation could be, for example, coefficients for powers of two representing the odd integer. The binary representation is then configured as comb bit-columns, wherein every bit-column is a signed odd integer. Another implementation applies this recoding method and discloses a variation of comb methods that computes elliptic curve point multiplication more efficiently and with less saved points than known comb methods. The disclosed point multiplication methods are then modified to be Simple Power Analysis (SPA)-resistant.
摘要:
The described implementations relate to establishing authenticated communication between a client computing device and a service provider. In one implementation, once a registration procedure is complete, multiple authentication servers are used by a client computing device and a service provider to facilitate the establishment of an authenticated communication session. However, the authentication servers are not necessarily trusted authorities. That is, secrets of the various described devices are not revealed to each other.
摘要:
A method and system is provided for encrypting an image compressed with a JPEG2000-based compression with minimal overhead so that the encrypted codestream is compliant with the syntax of the JPEG2000-based compression and can be scaled without decrypting. The encryption system generates, for each independent encryption segment of a codestream for an image, a unique initialization vector from a global initialization vector in such a way that the initialization vectors can be generated during decryption from the global initialization vector, even after truncation. The encryption system encrypts each independent encryption segment using its unique initialization vector. The encryption system ensures that the encrypted codestream is compliant with the syntax of the JPEG2000-based compression both as originally generated and as truncated by an encryption-unaware device.
摘要:
Systems and methods providing ciphertext switching for syntax compliant encryption are described. In one aspect, intermediate ciphertext is generated from syntax compliant plaintext. Post-processing is applied to the intermediate ciphertext to determine if there are any illegal symbols in the intermediate ciphertext. If an illegal symbol is located, the illegal symbol in the intermediate ciphertext is switched with a corresponding plaintext symbol. One or more iterations of the post-processing and switching operations result in syntax compliant ciphertext.
摘要:
Techniques for an image-based CAPTCHA for object recognition are described. The disclosure describes adding images to a database by collecting images by querying descriptive keywords to an image search engine or crawling images from the Internet.The disclosure describes generating the image-based CAPTCHA. The image is retrieved from the database, along with objects having significant values. An object is cropped from its image. The portion on the image where the object has been cropped is filled with image inpainting. The process obtains other objects from the database. The object is mixed among the other objects to form a set of candidate objects. A user is asked to select “the object” from the set of candidate objects that fits or matches the image. The image-based CAPTCHA evaluates whether a response, the selection, is from a human or a bot.
摘要:
A method and system is provided for encrypting an image compressed with a JPEG2000-based compression with minimal overhead so that the encrypted codestream is compliant with the syntax of the JPEG2000-based compression and can be scaled without decrypting. The encryption system generates, for each independent encryption segment of a codestream for an image, a unique initialization vector from a global initialization vector in such a way that the initialization vectors can be generated during decryption from the global initialization vector, even after truncation. The encryption system encrypts each independent encryption segment using its unique initialization vector. The encryption system ensures that the encrypted codestream is compliant with the syntax of the JPEG2000-based compression both as originally generated and as truncated by an encryption-unaware device.
摘要:
A fast and secure syntax compliant encryption schema, “locally iterative encryption,” can produce compliant ciphertext for a general syntax specification. In one implementation, an engine partitions a data stream into blocks, and encrypts each block iteratively until syntax compliance conditions are met. A system using the schema can utilize either stream ciphers or block ciphers in different modes. Locally iterative encryption methods are fast and remain at approximately the same speed even as the length of the data stream to be encrypted increases. Besides providing superior processing speed, the locally iterative encryption schema is also more robust to errors in the resulting ciphertext and in the resulting decrypted plaintext than conventional syntax compliant encryption techniques. Locally iterative encryption is secure as long as an underlying encryption cipher selected for use in the schema is secure.
摘要:
A flexible framework for generating “scalable layered access” codestreams allows a bitstream architect to select the number of access types and the number of access layers within each access type. At least some of the access layers are encrypted (or scrambled). Some of the access layers may be left unencrypted or unscrambled to allow free access to those layers. The framework facilitates simultaneous access of multimedia content by different users enjoying selective decryption of different access types and different access layers. An exemplary key schema for the framework sends only one or only a few keys to an end user for a given access layer, from which decryption keys for the content can be derived by hashing and then combining under a Group Diffie-Hellman key agreement. In one implementation, only one key is sent in a license to an end user and other partial key information for Group Diffie-Hellman combination with the licensed key is included in the publicly distributed codestream.
摘要:
The described implementations relate to establishing authenticated communication between a client computing device and a service provider. In one implementation, once a registration procedure is complete, multiple authentication servers are used by a client computing device and a service provider to facilitate the establishment of an authenticated communication session. However, the authentication servers are not necessarily trusted authorities. That is, secrets of the various described devices are not revealed to each other.