White-box cryptography encryption-decryption method based on expansion ciphertext

A white-box cipher and encryption method technology, applied in the field of white-box cipher encryption and decryption, can solve the problems of slow decryption speed and insecurity, and achieve high efficiency
CN106059752AInactive Publication Date: 2016-10-26INST OF INFORMATION ENG CAS
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
INST OF INFORMATION ENG CAS
Publication Date
2016-10-26
Estimated Expiration
Not applicable · inactive patent

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Abstract

The invention discloses a white-box cryptography encryption-decryption method based on an expansion ciphertext. The method comprises the expansion ciphertext and a lookup table, wherein a pseudorandom bit stream is implied in the expansion ciphertext; the lookup table is used for decrypting n bits to m bits (the n is greater than the m); and a table lookup operation is a combination of three functions, namely the one-to-one mapping function F <(K, n-n)> of n-bit inputs to n-bit outputs relevant to a secret key K, the function C<n-m> of the n-bit inputs to the n-bit outputs, and the one-to-one mapping function F <(K, m-m)> of m-bit inputs to m-bit outputs relevant to the secret key K. According to the method disclosed by the invention, in encryption, a server side takes the pseudorandom bit stream as a mask, is combined with the ciphertext and is scrambled to obtain the expansion ciphertext; and in decryption, the n-bit ciphertext is decrypted into a m-bit plaintext via the table lookup operation. The decryption efficiency can be obviously improved.
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Description

technical field

[0001] The invention belongs to the field of information technology, and relates to a white-box cipher encryption and decryption method based on expanded ciphertext, which can be applied in untrustworthy environments such as smart phones and digital set-top boxes. Background technique

[0002] Traditional cryptographic algorithms are always assumed to operate in a black-box environment at the beginning of design, that is, attackers can only observe the input and output of the algorithm. However, with the development of information technology, this assumption is no longer valid. Currently, various electronic devices are available everywhere and can directly or indirectly access the Internet, and there are more and more ways for people to obtain digital content. These devices include, but are not limited to, digital set-top boxes, IPTVs, PCs, and increasingly handheld devices such as mobile phones, tablet computers, and the like. With the intelligentization o...

Claims

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