網(wǎng)絡(luò)安全-electronicmailsecurity-資料下載頁
2024-10-17 11:27本頁面
【導(dǎo)讀】由個(gè)人發(fā)展起來——。PGP為電子郵件和文件存儲(chǔ)應(yīng)用提供了認(rèn)證和保密性服務(wù)。–算法的專利之爭(zhēng)。PGP快速發(fā)展和流行的原因。–建立在普遍認(rèn)為非常安全的算法的基礎(chǔ)上，算法的安全性已經(jīng)得到了充分的論證，如公鑰加密包括RSA、DSS. 為了適應(yīng)郵件的大小限制，消息用一次性會(huì)話密鑰加密，–接收者計(jì)算報(bào)文的散列碼，與解密得到的進(jìn)行比較，–對(duì)消息M生成一個(gè)新的散列碼，與H比較。簽名與消息可以分離。對(duì)稱加密算法和公鑰加密算法的結(jié)合可以縮。用公鑰算法解決了會(huì)話密鑰的單向分發(fā)問題。兩種服務(wù)都需要時(shí)，發(fā)送者先用自己的私鑰簽名。壓縮對(duì)郵件傳輸或存儲(chǔ)都有節(jié)省空間的好處。某些郵件系統(tǒng)只允許ASC字符，所以PGP提供了轉(zhuǎn)換到。采用了Radix-64轉(zhuǎn)換方案。PGP使用四種類型的密鑰：
【正文】 ational language‖ characters (nonASCII) – messages over a certain size – ASCII to EBCDIC translation problems – lines longer than a certain length (72 to 254 characters) Header Fields in MIME ? MIMEVersion: Must be ―‖ RFC 2045, RFC 2046 ? ContentType: More types being added by developers (application/word) ? ContentTransferEncoding: How message has been encoded (radix64) ? ContentID: Unique identifying character string. ? Content Description: Needed when content is not readable text (., mpeg) MIME內(nèi)容類型 MIME轉(zhuǎn)換編碼 S/MIME Functions ? Enveloped Data: Encrypted content and encrypted session keys for recipients. ? Signed Data: Message Digest encrypted with private key of ―signer.‖ ? ClearSigned Data: Signed but not encrypted. ? Signed and Enveloped Data: Various orderings for encrypting and signing. Algorithms Used ? Message Digesting: SHA1 and MDS ? Digital Signatures: DSS ? SecretKey Encryption: TripleDES, RC2/40 (exportable) ? PublicPrivate Key Encryption: RSA with key sizes of 512 and 1024 bits, and DiffieHellman (for session keys). S/MIME密碼操作函數(shù) MIME 消息內(nèi)容類型 S/MIME Certificate Processing ? S/MIME uses v3 certificates ? Managed using a hybrid of a strict CA hierarchy amp。 PGP’s web of trust ? Each client has a list of trusted CA’s certs and own public/private key pairs amp。 certs ? Certificates must be signed by trusted CA’s Certificate Authorities ? Have several wellknown CA’s ? Verisign is one of most widely used ? Verisign issues several types of Digital IDs ? With increasing levels of checks amp。 hence trust Class Identity Checks Usage 1 name/ check web browsing/ 2+ enroll/addr check , subs, s/w validate 3+ ID documents ebanking/service access VeriSign公鑰證書類型 S/MIME郵件用法 (一 ) ? 公鑰管理 S/MIME郵件用法 (二 ) ? 私鑰管理 S/MIME郵件用法 (三 ) ? 把帳號(hào)與私鑰關(guān)聯(lián)起來 S/MIME郵件用法 (四 ) ? 撰寫郵件
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