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SHA-1 and DNS in 2005

SHA-1 and DNS in 2005. [ lafur Gu x mundsson DNSEXT co-chair. IETF-62 March 2005 ogud@ogud.com. SHA-1 collision attack. Takes less time to find two sets of data that have same SHA-1 signature It was assumed to take around 2^80 attempts Attack reduces to 2^69. Still a real long time.

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SHA-1 and DNS in 2005

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  1. SHA-1 and DNS in 2005 [lafur Guxmundsson DNSEXT co-chair IETF-62 March 2005 ogud@ogud.com

  2. SHA-1 collision attack • Takes less time to find two sets of data that have same SHA-1 signature • It was assumed to take around 2^80 attempts • Attack reduces to 2^69. • Still a real long time. • Not known if the attack works on >structured= data such as DNS RR=s and DNS messages. • Attacks only get better • Hardware gets better • Trivial to distribute effort • HMAC is resistant to this attack

  3. Where is SHA-1 used in DNS • RRSIG • TSIG (proposed) • DS

  4. RRSIG • Resiliane: • Digest covers structed data • DNS SIG header • DNS RR header • DNS RR=s • Digest covers some Arandom data@ • Time signed and expiry • Data is known/valid for a limited time. • RRSIG risk is low

  5. TSIG/SHA1 • Resiliance: • Covers Arandom@ data • Time signed and fudge • HMAC of query. • Valid for a real short time (300 s) • Uses HMAC • Threat level: extremly low

  6. DS • Long lived simple SHA-1 digest • Mitigating factors • Covers name • Digest must cover useable new key. • Key generation is harder than calculating new digest on random data • Risk: Low to medium

  7. Going forward • DS: • Plan effort to add a second digest • Not sure which one to pick • wait for security area guidance • Transition/Rollover issues • Not needed in near term • RRSIG • Think about adding new digests to RSA and ECC • Not needed anytime soon. • TSIG • Proposal mandating implementation of SHA-256 • Not realy needed but harmless

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