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S/MIME information and links
last changed 980613
S/MIME is a protocol to implement security for a communication via TCP/IP. We have here some information and links.
 
S/MIME what it is and how it works. S/MIME references and links
How does S/MIME work ?
S/MIME is developed by RSA Data Security INC . 
S/MIME is built on proven crypthographic constructs and is a extension of the MIME specification. 
Has a high interoperability betweeen products from different vendors. 
Based on the PKCS #7 data format for messages, X.509v3 format for certificates. 
No additional applications, utilities or DOS shells are required, all of the security is built directly into the applications and with an easy-to-use interface 
High exportability, key size is dynamic 

Overview of the process: 
A sends a message to B. 

A: 
Message * A:s message intendent for B. 
1: Hash(message)    -method: MD5 * Digital fingerprint. 
2: Encrypt k (digitalfingerprint)    -k = A:s private key    -method: RSA * Digital signature which assures authenticity for the message.This digital signature can now be sent or encrypted for privacy. 
3: Encrypt k (digital signature)    -k = symmetric key    -methods: 3DES                   RC2 * Produces some randomly encrypted content and its corresponding "passphrase" 
4: Encrypt k ("passphrase")    -k = B:s public key * The message is ready for transport! 

B: 
1: Dekrypt k ("passphrase")    -k = B:s private key * Symmetric key to expose the encrypted content. 
2: Dekrypt k ("encrypted content")   -k = symmetric key  * Clear message, digital signature 
3: Dekrypt k (digital signature)   -k = A:s public key * Digital fingerprint 
4: Hash(message)    -method: MD5 * Digital fingerprint. 
5: Compare the two fingerprints * If identical * OK 

 S/MIME  Commercial S/MIME 

References:

 S/MIME Version 3 Message specification: draft, March 24, 1998,   HYPERLINK    http://www.imc.org/draft-ietf-smime-msg 

   S/MIME Version 3 Certificate Handling draft, March 24, 1998   HYPERLINK    http://www.imc.org/draft-ietf-smime-cert 

  How does the S/MIME encryption and digital signature process work?,   HYPERLINK    http://download.worldtalk.com/support/client/crypfaq.htm#smime 

  S/MIME central.   HYPERLINK http://www.rsa.com/smime/    
 

Created by Micke Pettersson, mikael.pettersson@tsl.uu.se, http://www3.tsl.uu.se/~micke