Smime tells about mime contents and itsnew feature

secure mime

1. S/MIME

2. Henric Johnson 2 S/MIME Secure/Multipurpose Internet Mail Extension S/MIME will probably emerge as the industry standard. The protocol is an enhancement of the Multipurpose Internet Mail Extension (MIME) protocol . It can send messages only in NVT 7-bit ASCII format. MIME is a supplementary protocol that allows non-ASCII data to be sent through e-mail. MIME transforms non-ASCII data at the sender site to NVT ASCII data and delivers it to the client MTA to be sent through the Internet .

3. Henric Johnson 4 Header fields in MIME MIME-Version: Must be “1.0” Content-Type : More types being added by developers (application/word) Content-Transfer-Encoding: How message has been encoded (radix-64) Content-ID: Unique identifying character string. Content Description: Needed when content is not readable text ( e.g.,mpeg )

4. Henric Johnson 7 S/MIME Content type S/MIME adds some new content types to include security services to the MIME . . All new types include the parameter “application/pkcs7-mime,” in which “ pkcs ” defines “Public Key Cryptography Specification .” Enveloped Data: Encrypted content and session keys for recipients. Signed Data: Message Digest encrypted with private key of “signer.” Clear-Signed Data: Signed but not encrypted. Signed and Enveloped Data: Various orderings for encrypting and signing.or Digest Data content type.

5. Henric Johnson 13 Algorithms Used Message Digesting: SHA-1 and MDS Digital Signatures: DSS Secret-Key Encryption: Triple-DES, RC2/40 Public-Private Key Encryption: RSA with key sizes of 512 and 1024 bits, and Diffie -Hellman (for session keys).

6. Henric Johnson 14 Key management The key management in S/MIME is a combination of key management used by X.509 and PGP. S/MIME uses public-key certificates signed by the certificate authorities defined by X.509 . the user is responsible to maintain the web of trust to verify signatures as defined by PGP.