Microsoft Technology Licensing, LLC

Oren Ish-am

Yevgeny Yankilevich

Vadim Makhervaks

Robert Groza, Jr

Yi Yuan

Michael Milkov

A computing system uses Advanced Encryption Standard XEX Based Tweaked Codebook Mode with Ciphertext Stealing (AES-XTS) encryption to encrypt a block of data using a tweak key, a data key, a modified tweak value, and the block of data to thereby generate an encrypted block of data. The modified tweak value is computed according to the expression DEC(0, CONST KEY), where DEC is an AES decryption algorithm, and CONST KEY is the tweak key. The encrypted block of data is thereby formatted according to the Advanced Encryption Standard with no extended mode and not according to the XEX Based Tweaked Codebook Mode with Ciphertext Stealing.

Encryption system and method

A computing system uses AES-XTS encryption to encrypt data of a first part of first data stream using a tweak key, a data key, an initial tweak value, in a first encryption session, store the encrypted first part, then encrypts a second part of the first data stream in a second encryption session commenced after the termination of the first encryption session; and store the encrypted second part in the encrypted data store. The second part of the first data stream is encrypted using a modified tweak value computed based on the initial tweak value, the tweak key, and a block index of a last cipher block of the first part of the first data stream.

System and method for incremental encryption

A method supporting interleaved authentication-encryption operations for different data records provides for constructing authentication tag usable to authenticate a transmitted data record from multiple different tag segments generated by an authentication-encryption engine in association with different segments of the data record. The method provides for recovering a first partial tag from a first segment tag received from an authentication-encryption engine by performing one or more operations effective to reverse certain operations performed by the third-party authentication-encryption engine. One or more additional partial tags may be similarly recovered from additional tag segments subsequently output from the third-party authentication-encryption engine in association with the data record, and a complete authentication tag for the data record may be generated based on the recovered first partial tag and each of the one or more additional recovered partial tags.

Partial authentication tag aggregation to support interleaved encryption and authentication operations on multiple data records

A method provides for receiving multiple different segment tags generated based on different segments of a data record, where each segment is encrypted during a separate encryption process. Upon receipt, each of the multiple different segment tags is adjusted by an end-of-segment operation that induces a segment-specific error rendering the segment tag invalid for authentication of the data record as a whole. The method provides for accumulating together the multiple different segment tags to form a combined multi-segment tag, computing a correction effective to reverse a cumulative effect of the segment-specific error for each of the multiple different segment tags on the combined multi-segment tag; and generating a complete authentication tag by adjusting the combined multi-segment tag based on the computed correction. The complete authentication tag is usable to authenticate aspects of the data record as a whole.

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Haifa, Israel

Oren Ish-am