2. Bounce Address Tag Validation (BATV) D. Crocker IETF J. Levine San Diego Sam Silberman 2004 Tony Finch MASS BOF D. Crocker IETF J. Levine San Diego Sam Silberman 2004 Tony Finch MASS BOF

3. 2 2 D. Crocker, Brandenburg InternetWorkingBATV, IETF San Diego 2004 BATV – Detecting forged MailFrom  Digital signature  Key based on RHS domain  Permit multiple schemes (Sorry, but no choice)  Meta-syntax on LHS (local-part) for parameters  Permits finding mailbox without understanding sig  Hard limit of 64 bytes for total of local-part  Digital signature  Key based on RHS domain  Permit multiple schemes (Sorry, but no choice)  Meta-syntax on LHS (local-part) for parameters  Permits finding mailbox without understanding sig  Hard limit of 64 bytes for total of local-part mailbox@example.com  batv=mailbox/scheme/parms@example.com

4. 3 3 D. Crocker, Brandenburg InternetWorkingBATV, IETF San Diego 2004 Bounce Address Evaluation Venues MSA MTAMTA MDA MTA MDA MTA Bounce Receipt Original Relay Bounce Generation

5. 4 4 D. Crocker, Brandenburg InternetWorkingBATV, IETF San Diego 2004 Base Scheme – PSB0 Base Scheme – PSB0  Private Signed Bounce zero  Detected invalid received bounces  Interpreted only by issuer  Limited replay protection  Private Signed Bounce zero  Detected invalid received bounces  Interpreted only by issuer  Limited replay protection sig-val = key-id encrypt (, timestamp, random-string )

6. 5 5 D. Crocker, Brandenburg InternetWorkingBATV, IETF San Diego 2004 Approach for Public Key Scheme  Detect at time of bounce generation, or earlier  Based on content standard, when available  Use all of the mechanism, but tune computation to MailFrom limitations  E.g., hash the signature into a short string.  Detect at time of bounce generation, or earlier  Based on content standard, when available  Use all of the mechanism, but tune computation to MailFrom limitations  E.g., hash the signature into a short string.