網(wǎng)絡安全-electronicmailsecurity-預覽頁
【正文】 of binary data to textual form – S/MIME added security enhancements ? Have S/MIME support in various modern mail agents: MS Outlook, Netscape etc S/MIME的 功能 ? 提供了簽名和加密消息的功能 – Enveloped data： 包含郵件加密之后的內(nèi)容，以及針對一個或多個接收者的加密密鑰 – Signed data： 對簽名內(nèi)容作消息摘要，然后用簽名者的私鑰對摘要加密，以此形成一個數(shù)字簽名；內(nèi)容與簽名被轉(zhuǎn)換成 base64編碼，一個簽名的數(shù)據(jù)消息只能被具有 S/MIME能力的接收者查看 – Clearsigned data： 只有簽名部分用 base64編碼，結(jié)果是，即使接收者沒有 S/MIME能力，他也能查看消息內(nèi)容，只是他不能驗證該簽名 – Signed and enveloped data： 簽名和加密的結(jié)合，加密數(shù)據(jù)被簽名或者簽名數(shù)據(jù)被加密 Simple Mail Transfer Protocol (SMTP, RFC 822) ? SMTP Limitations Can not transmit, or has a problem with: – executable files, or other binary files (jpeg image) – ―national 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 am
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