Secure Mail Transfer Protocol (SecMTP). Hathai Tanta-ngai, Tony Abou-Assaleh, Sittichai Jiampojamarn, and Dr. Nick Cercone Faculty of Computer Science Dalhousie University. Overview. Introduction Current email security Secure Mail Transfer Protocol Discussion Conclusion Future work. - PowerPoint PPT Presentation
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Secure Mail Transfer Protocol Secure Mail Transfer Protocol (SecMTP)(SecMTP)Secure Mail Transfer Protocol Secure Mail Transfer Protocol (SecMTP)(SecMTP)
OverviewOverview
Assumption and LimitationAssumption and Limitation
Incorporate security procedure into SMTPIncorporate security procedure into SMTP
Maintain the simplicity and compatibility that Maintain the simplicity and compatibility that SMTP providesSMTP provides
Achieve the five security goals: Achieve the five security goals: confidentiality, integrity, authentication, non-confidentiality, integrity, authentication, non-repudiation, and certificationrepudiation, and certification
Assumption and LimitationAssumption and LimitationAssumption and LimitationAssumption and Limitation
All SecMTP compliant servers must be All SecMTP compliant servers must be properly certifiedproperly certifiedNon-repudiation has to be implementedNon-repudiation has to be implementedSecMTP user trusts the integrity of the end SecMTP user trusts the integrity of the end servers but not the intermediate connectionservers but not the intermediate connection
We designed SecMTP’s architecture, protocol We designed SecMTP’s architecture, protocol specifications, and SecMTP Extension Service specifications, and SecMTP Extension Service to SMTPto SMTP
The SecMTP User Requested Options The SecMTP User Requested Options The SecMTP User Requested Options The SecMTP User Requested Options
Receiver public key encryptionReceiver public key encryption
Sender private key digital signatureSender private key digital signature
Restrict optionRestrict option
Seamless interfaces Seamless interfaces Users private/public keys are stored at the server Users private/public keys are stored at the server machinemachine
The State Diagram of Starting a The State Diagram of Starting a SecMTP ConnectionSecMTP ConnectionThe State Diagram of Starting a The State Diagram of Starting a SecMTP ConnectionSecMTP Connection
SMTP Extension Service for Secure SMTP Extension Service for Secure Mail Transfer Protocol (SecMTP)Mail Transfer Protocol (SecMTP)SMTP Extension Service for Secure SMTP Extension Service for Secure Mail Transfer Protocol (SecMTP)Mail Transfer Protocol (SecMTP)
1.1. The name of the SMTP service extension is The name of the SMTP service extension is “Secure Mail Transfer Protocol”“Secure Mail Transfer Protocol”
2.2. The EHLO keyword value associated with The EHLO keyword value associated with the extension is SECMTPthe extension is SECMTP
3.3. No parameters are allowed with this EHLO No parameters are allowed with this EHLO keyword valuekeyword value
SMTP Extension Service for Secure SMTP Extension Service for Secure Mail Transfer Protocol (SecMTP)Mail Transfer Protocol (SecMTP)SMTP Extension Service for Secure SMTP Extension Service for Secure Mail Transfer Protocol (SecMTP)Mail Transfer Protocol (SecMTP)
4.4. Three option parameters are added to the Three option parameters are added to the RCPT command:RCPT command:
SIGNSIGN: digitally sign message header consisting of a : digitally sign message header consisting of a message digest and sender identitymessage digest and sender identity
ENCRENCR: encrypt the message with receiver public key: encrypt the message with receiver public key
STRICTSTRICT: only transfer the message through properly : only transfer the message through properly authenticated and certified SecMTP serversauthenticated and certified SecMTP servers
5.5. No additional SMTP verbs are defined by No additional SMTP verbs are defined by this extensionthis extension
S: <waits for connection on TCP port 25>S: <waits for connection on TCP port 25>C: <opens connection>C: <opens connection>S: 220 foo.com SMTP service readyS: 220 foo.com SMTP service readyC: EHLO bar.comC: EHLO bar.com
......C: STARTTLSC: STARTTLSC \& S: <negotiate a TLS session>C \& S: <negotiate a TLS session>C \& S: <check result of negotiation>C \& S: <check result of negotiation>C: EHLOC: EHLOS: 250 ... AUTH CRAM-MD5 DIGEST-MD5 ...S: 250 ... AUTH CRAM-MD5 DIGEST-MD5 ...C: AUTH CRAM-MD5C: AUTH CRAM-MD5S: 334 ...S: 334 ...
Example (cont.)Example (cont.)Example (cont.)Example (cont.)
C: DATAC: DATAS: 354 Start mail input; end with <CRLF>.<CRLF>S: 354 Start mail input; end with <CRLF>.<CRLF>C: Data data data...C: Data data data...C: ...etc. etc. etc.C: ...etc. etc. etc.C: .C: .S: 250 OKS: 250 OKC: QUITC: QUITS: 221 foo.com Service closing transmission channelS: 221 foo.com Service closing transmission channel
ShortcomingsShortcomingsNon-SecMTP clients need to examine the security Non-SecMTP clients need to examine the security information manuallyinformation manually
Encryption and decryption are done at the serverEncryption and decryption are done at the server
Users must trust the end servers to provide security Users must trust the end servers to provide security servicesservices
The SecMTP servers may become bottleneckThe SecMTP servers may become bottleneck
SecMTP compliant clients and servers are required SecMTP compliant clients and servers are required to achieve full benefit of SecMTPto achieve full benefit of SecMTP