【信息安全工程师201805】【70】利用公开密钥算法进行数据加密时，采用的方式是（70）。

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【信息安全工程师201805】【66】下列关于公钥密码体制说法不正确的是（66）。

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【信息安全工程师201805】【50】网络系统中针对海量数据的加密，通常不采用（50）方式。

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【信息安全工程师202011】【71-75】Symmetric-key cryptosystems use the（71） key for encryption and decryption of a message,though a message or group of messages may have a different key than others. A significant disadvantage of symmetric ciphers is the key management necessary to use them securely.Each distinct pair of communicating parties must, ideally, share a different key, and perhaps each ciphertext exchanged as well. The number of keys required increases as the square of the number of network members,which very quickly requires complex key management schemes to keep them all straight and secret. The difficulty of securely establishing a secret（72）between two communicating parties, when a secure channel doesn't already exist between them, also presents a chicken-and-egg problem which is a considerable practical obstacle for cryptography users in the real worl
Whitfield Difñie and Martin Hellman, authors of the first paper on public-key cryptography.
In a groundbreaking 1976 paper, Whitfield Diffie and Martin Hellman proposed the notion of public-key (also, more generally, called asymmetric key) cryptography in which two different but mathematically related keys are used-a public key and a private key. A public key system is so constructed that calculation of one key (the private key) is computationally infeasible（73）the other (the public key), even though they are necessarily relate Instead, both keys are generated secretly, as an interrelated pair. The historian David Kahn described public-key cryptography as “the most revolutionary new concept in the field since poly-alphabetic substitution emerged in the Renaissance”.
In public-key cryptosystems,the（74）key may be freely distributed,while its paired private key must remain secret. The public key is typically used for encryption, while the private or secret key is used for decryption. Diffie and Hellman showed that public-key cryptography was possible by presenting the Diffie-Hellman key exchange protocol.
In 1978, Ronald Rivest, Adi Shamir, and Len Adleman invented（75）,another public-key system.
In 1997, it finally became publicly known that asymmetric key cryptography had been invented by James H. Ellis at GCHQ,a British intelligence organization, and that, in the early 1970s,both the Diffie-Hellman and RSA algorithms had been previously developed(by Malcolm J. Williamson and Clifford Cocks, respectively).

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【信息安全工程师202111】【15】密码算法可以根据密钥属性的特点进行分类，其中发送方使用的加密密钥和接收方使用的解密密钥不相同，并且从其中一个密钥难以推导出另一个密钥，这样的加密算法称为（15）。

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