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The Diffie–Hellman problem (DHP) is a mathematical problem first proposed by Whitfield Diffie and Martin Hellman in the context of cryptography. The motivation for this problem is that many security systems use mathematical operations that are fast to compute, but hard to reverse. For example, they enable encrypting a message, but reversing the encryption is difficult. If solving the DHP were easy, these systems would be easily broken. == Problem description == The Diffie–Hellman problem is stated informally as follows: : Given an element ''g'' and the values of ''gx'' and ''gy'', what is the value of ''gxy''? Formally, ''g'' is a generator of some group (typically the multiplicative group of a finite field or an elliptic curve group) and ''x'' and ''y'' are randomly chosen integers. For example, in the Diffie-Hellman key exchange, an eavesdropper observes ''gx'' and ''gy'' exchanged as part of the protocol, and the two parties both compute the shared key ''gxy''. A fast means of solving the DHP would allow an eavesdropper to violate the privacy of the Diffie-Hellman key exchange and many of its variants, including ElGamal encryption. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Diffie–Hellman problem」の詳細全文を読む スポンサード リンク
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