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 (밥의 공개 키)
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밥은 두 개의 키를 받고있다. 밥의 열쇠 중 하나는 다른 하나는 개인 키라고, 공개 키라고합니다.
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사람은 밥의 공개 키를 얻을 수 있지만, 밥은 자신에게 자신의 개인 키를 유지
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| 가볍게 두드리기 | 더그 | 수잔 | ||
밥의 공개 키는 그것을 필요로 누구나 사용할 수 있지만 그는 자신에게 자신의 개인 키를 유지합니다. 키 정보를 암호화하는 데 사용됩니다. 정보를 암호화하면 해당 키를 가진 사람 만이 다시 읽을 수 있도록, "그것을 스크램블링"를 의미한다. Bob의 두 키 중 하나는 데이터를 암호화 할 수 있으며, 다른 키는 데이터의 암호를 해독 할 수 있습니다.
(아래 그림 참조) 수잔은 밥의 공개 키를 사용하여 메시지를 암호화 할 수 있습니다. 밥은 메시지를 해독하기 위해 자신의 개인 키를 사용합니다. 밥의 동료 중 어떤 수잔이 암호화 된 메시지에 액세스 할 수 있지만 Bob의 개인 키없이 데이터가 쓸모있다.
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"이봐 밥, 어떻게 타코 벨에서 점심 식사에 대한. 나는 그들이 무료로 리필이 들어!" |  |
HNFmsEm6Un BejhhyCGKOK JUxhiygSBCEiC 0QYIh / Hn3xgiK BcyLK1UcYiY lxx2lCFHDC / A |
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HNFmsEm6Un BejhhyCGKOK JUxhiygSBCEiC 0QYIh / Hn3xgiK BcyLK1UcYiY lxx2lCFHDC / A |  |
"이봐 밥, 어떻게 타코 벨에서 점심 식사에 대한. 나는 그들이 무료로 리필이 들어!" |
자신의 개인 키와 올바른 소프트웨어, 밥은 문서 및 기타 데이터에 디지털 서명을 넣을 수 있습니다. 디지털 서명은 "스탬프"밥은 밥에 고유 한 데이터를 배치하고, 위조하기가 매우 어렵다. 또한, 서명은 변경 사항이 발견되지 않을 수없는 서명 된 데이터에 대한 것을 보장합니다.
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To sign a document, Bob's software will crunch down the data into just a few lines by a process called "hashing". These few lines are called a message digest. (It is not possible to change a message digest back into the original data from which it was created.) |
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Bob's software then encrypts the message digest with his private key. The result is the digital signature.
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Finally, Bob's software appends the digital signature to document. All of the data that was hashed has been signed.
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Bob now passes the document on to Pat.
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First, Pat's software decrypts the signature (using Bob's public key) changing it back into a message digest. If this worked, then it proves that Bob signed the document, because only Bob has his private key. Pat's software then hashes the document data into a message digest. If the message digest is the same as the message digest created when the signature was decrypted, then Pat knows that the signed data has not been changed. |
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Doug (our disgruntled employee) wishes to deceive Pat. Doug makes sure that Pat receives a signed message and a public key that appears to belong to Bob. Unbeknownst to Pat, Doug deceitfully sent a key pair he created using Bob's name. Short of receiving Bob's public key from him in person, how can Pat be sure that Bob's public key is authentic? |
It just so happens that Susan works at the company's certificate authority center. Susan can create a digital certificate for Bob simply by signing Bob's public key as well as some information about Bob.
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Now Bob's co-workers can check Bob's trusted certificate to make sure that his public key truly belongs to him. In fact, no one at Bob's company accepts a signature for which there does not exist a certificate generated by Susan. This gives Susan the power to revoke signatures if private keys are compromised, or no longer needed. There are even more widely accepted certificate authorities that certify Susan.
Let's say that Bob sends a signed document to Pat. To verify the signature on the document, Pat's software first uses Susan's (the certificate authority's) public key to check the signature on Bob's certificate. Successful de-encryption of the certificate proves that Susan created it. After the certificate is de-encrypted, Pat's software can check if Bob is in good standing with the certificate authority and that all of the certificate information concerning Bob's identity has not been altered.
Pat's software then takes Bob's public key from the certificate and uses it to check Bob's signature. If Bob's public key de-encrypts the signature successfully, then Pat is assured that the signature was created using Bob's private key, for Susan has certified the matching public key. And of course, if the signature is valid, then we know that Doug didn't try to change the signed content.
Although these steps may sound complicated, they are all handled behind the scenes by Pat's user-friendly software. To verify a signature, Pat need only click on it.
(c) 1996, David Youd
Permission to change or distribute is at the discretion of the author
Warning: You may be missing a few lines of text if you print this document. This seems to occur on pages following pages that have blank space near the bottom due to moving tables with large graphics in them to the next page so that the images are not split across pages. If this happens to you, simply print out document in sections. (Ex: I have the problem on page 4, so I print pages 1-3, then pages 4-5.)
