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Device, method, and program for encryption and decryption and recording medium

An encryption method and technology of an encryption device, which are applied to encryption devices with shift registers/memory, secure communication devices, synchronous transmission/reception encryption devices, etc., can solve problems such as difficult video data

Inactive Publication Date: 2006-04-12
NAT INST OF INFORMATION & COMM TECH
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  • Abstract
  • Description
  • Claims
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Problems solved by technology

This document describes packet communication as an object, so there is a problem that it is difficult to use for continuous streams such as video data and music data.
In order to synchronize streaming data, a synchronization signal is required, but it is not described in JP-A-2000-224158

Method used

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  • Device, method, and program for encryption and decryption and recording medium
  • Device, method, and program for encryption and decryption and recording medium
  • Device, method, and program for encryption and decryption and recording medium

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Embodiment Construction

[0040] The best way to implement the invention

[0041] Fig. 3 schematically shows the encryption device of the present invention. Reference numeral 11a denotes an "exclusive OR" gate (hereinafter, abbreviated as EX-OR gate) for inputting an IV having the same bit length as the encryption key of the stream cipher extracted from the encrypted file. Enter the common key 12a for the EX-OR gate 11a. The common key 12a is a secret key shared by the transmitting side and the receiving side.

[0042] How to extract the IV from the ciphertext can be decided in advance on the sending side and the receiving side. For example, when encrypting video data, it may be determined in advance from a designated position within one frame, for example, from the top of the effective video data of one frame to use the designated number of bits as the IV. In this case, the time interval is the frame period.

[0043] The encryption key 13a is obtained from the output of the EX-OR gate 11a, and the data to...

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Abstract

Data of a part of a ciphertext of a previous time is acquired as IV and calculated with a common key at an EX-OR gate to obtain an encryption key. By using this encryption key, data to be transmitted is encrypted according to the stream encryption. If encrypted data is obtained at time tn-1, next, IV acquired from the encrypted data is supplied to the EX-OR gate and an exclusive OR with a common key is obtained, thereby obtaining an encryption key. An exclusive OR is obtained between the encryption key and the transmission data, thereby performing stream encryption and obtaining encrypted data at time tn. Next, by using the IV acquired from the encrypted data, encryption at time tn+1 is performed. Hereinafter, at each time, encryption is repeated by using a part of the generated ciphertext as the IV.

Description

Technical field [0001] The present invention relates to an encryption and decryption device, method, program, and recording medium used for stream encryption. Background technique [0002] With the rapid spread of the Internet and mobile communications in recent years, opportunities for transmitting various data through wireless communications are increasing. Since a third party can simply monitor and eavesdrop on wireless communications, encryption of sent data is essential. As a cryptographic technique, a common key method that uses the same secret key in encryption and decryption is known, and there are block ciphers and stream ciphers in the common key method. [0003] Fig. 1A is a diagram illustrating a block cipher. The information bit string of the plaintext is divided into specified lengths (packets), and encrypted by the encryptor 1 in blocks. The ciphertext is also divided into groups. [0004] On the other hand, as shown in FIG. 1B, for the stream cipher, the random nu...

Claims

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Application Information

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IPC IPC(8): H04L9/18
CPCH04L9/065H04L2209/125H04L9/18H04L9/12
Inventor 长谷川晃朗金成主梅野健
Owner NAT INST OF INFORMATION & COMM TECH
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