Security and authen.ca.on
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1 Security and authen.ca.on more shadow root:$6$1z2.cqoj$bib7hoc7byvsvclmpc1c5f/h.gaddflg1xa2fqknmaoabwzi1ysldik2gikuebeo ugj33w8h4qdiwyvamlfij2eu.:15138:0:99999:7::: daemon:*:15040:0:99999:7::: keithwork:$6$crdefvr2q$b8.0j5p/7tvualkffaffe5a234.ggnfbgrfhkb6.jptn223zmja0ilte 1FoE6vzlf7Rt/eiNBSqfeegEVxs33fe#f7x0:15135:0:99999:7::: mysql:!:15087:0:99999:7::: httpd:!:15133:0:99999:7::: keithbackup:$6$whke4gjt$yumfe4gywhp656rnqv/7see8y5af/vgra3fue.g4facg4iug4vyjlg4f bgezw0i7feqmpchqpbsji/:15164:0:99999:7::: CSCI 470: Web Science Keith Vertanen Copyright 2014
2 Authen-ca-on Passwords One- way hashing Sal-ng passwords Overview Other forms: tokens, biometrics Digital signing Public key based signing PKI, CA PreDy Good Privacy (PGP) Securing web commerce SSL / TLS hdps 2
3 Proving your iden-fy Authen-ca-on Something you know: password, PIN, pet's name Something you possess: a key, smart card Something you are: fingerprints, re-na, face Something you do: voice print, handwri-ng, typing rhythm Means of authen-ca-on Password Token- based Biometric 3
4 Password authen-ca-on Users choose some secret password Differing levels of required complexity/annoyance hdps://xkcd.com/936/ 4
5 User ID and password Password storage Must be stored somewhere, e.g. /etc/passwd Shadow password file, e.g. /etc/shadow Reachable only by privileged users % more passwd root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/bin/sh work:x:1000:1000::/home/work:/bin/sh mysql:x:104:110:mysql Server,,,:/nonexistent:/bin/false httpd:x:1001:1001::/home/httpd:/bin/sh backup:x:1005:1005::/home/backup:/bin/sh % more shadow root:$6$1z2.cqoj$bib7hoc7byvsvclmpc1c5f/h.gaddflg1xa2fqknmaoabwzi1ysldik2gikuebeo ugj33w8h4qdiwyvamlfij2eu.:15138:0:99999:7::: daemon:*:15040:0:99999:7::: work:$6$crdefvr2q$b8.0j5p/7tvualkffaffe5a234.ggnfbgrfhkb6.jptn223zmja0ilte 1FoE6vzlf7Rt/eiNBSqfeegEVxs33fe#f7x0:15135:0:99999:7::: mysql:!:15087:0:99999:7::: httpd:!:15133:0:99999:7::: backup:$6$whke4gjt$yumfe4gywhp656rnqv/7see8y5af/vgra3fue.g4facg4iug4vyjlg4f bgezw0i7feqmpchqpbsji/:15164:0:99999:7::: 5
6 Hashing Normal hash func-ons: Key: large data set of variable length Value: small data set of fixed length Examples: Error checking: checksum, CRC Constant -me data structures: Java HashMap 6
7 Secure hashing Secure hash func-ons: Hash H(x) easy to compute for x One- way: given h=h(x) intractable to find x e.g. MD5 (128 bits), SHA- 1 (160 bits), SHA- 256 (256 bits), SHA- 512 (512 bits) 7
8 Desirable proper-es Secure hashing Pre- image resistant, one- way For any code h, intractable to find x s.t. H(x) = h 2 nd pre- image resistant, weak collision resistant For any block x, intractable to find y x s.t. H(y) = H(x) Strong collision resistant Uses: Intractable to find any pair (x, y) s.t. H(x) = H(y) One- way encryp-on of passwords: store only hash Intrusion detec-on: detect changes in file Digital signing of messages 8
9 History: 1991: MD5 by Ron Rivest 1993: SHA : Revised version, SHA : Flaw found in MD5 2005: ADack found on SHA : NIST required federal agencies to move to SHA : NIST selects Keccak for SHA- 3 hdp://blogs.technet.com/b/srd/archive/2012/06/06/more- informa-on- about- the- digital- cer-ficates- used- to- sign- the- flame- malware.aspx One itera-on within the SHA- 1 compression func-on: A, B, C, D and E are 32- bit words of the state F is a nonlinear func-on that varies <<< n denotes a leh bit rota-on by n places n varies for each opera-on W t is the expanded message word of round t K t is the round constant of round t Box with plus denotes addi-on modulo 2 32 hdp:// ca/ 9
10 ADacking passwords If hashed passwords compromised, adacker: Knows users with same password Can tell if user has same password on mul-ple systems (if using same hash func-on) Can use an offline dic-onary adack Dic-onary adack: Precompute hash value for: All sequences of a given (short) length Common words Check for match against hash in password file 10
11 Sal-ng passwords Salt On account crea-on, assign salt value: Timestamp, random value,... Salt stored unencrypted, associated with user ID Hash computed from salt plus user's password Makes dic-onary adack much more expensive % more shadow root:$6$1z2.cqoj$bib7hoc7byvsvclmpc1c5f/h.gaddflg1xa2fqknmaoabwzi1ysldik2gikuebeo ugj33w8h4qdiwyvamlfij2eu.:15138:0:99999:7::: daemon:*:15040:0:99999:7::: work:$6$crdefvr2q$b8.0j5p/7tvualkffaffe5a234.ggnfbgrfhkb6.jptn223zmja0ilte 1FoE6vzlf7Rt/eiNBSqfeegEVxs33fe#f7x0:15135:0:99999:7::: mysql:!:15087:0:99999:7::: httpd:!:15133:0:99999:7::: backup:$6$whke4gjt$yumfe4gywhp656rnqv/7see8y5af/vgra3fue.g4facg4iug4vyjlg4f bgezw0i7feqmpchqpbsji/:15164:0:99999:7::: $6 = SHA
12 Improving password security Reac-ve password checker: System adacks itself, revokes guessed passwords But system has to do an expensive amount of work Proac-ve password checker: Users selects a candidate password System checks if allowable Hopefully guide users to secure choice Without too much annoyance But different systems have: Different min/max lengths, allowed symbols, case rules, number rules,... 12
13 Improving password security User educa-on Encourage/force longer more complex passwords e.g. Users ohen mistakenly believe reversing word makes password unguessable Use first leder of personal phrase "My dog's first name is Rex" - > "MdfniR" Use random collec-on of words "correcthorsebaderystaple" Computer- generated passwords Normally low acceptance, users write them down Generate pronounceable syllables, FIPS PUB
14 Token- based authen-ca-on Require users possess some object Unique ID based Magne-c strip, embedded microprocessor,... e.g. ATM card, mobile phone (two factor) Ohen in combina-on with user knowledge e.g. ATM PIN 14
15 Biometric authen-ca-on PaDern recogni-on based Facial recogni-on: loca-on of facial features Fingerprints: ridges and furrows on finger-p Hand geometry: shape, length, width of fingers Re-nal: veins beneath re-nal surface Iris: structure of the iris Signature: style of handwri-ng Voice: paderns in speech signal Verifica-on: proving you are who you say Iden-fica-on: find out who you are 15
16 Biometric characteris-cs Cost Hand Signature Face Re.na Finger Iris Voice Accuracy 16
17 hdp:// hdp://i.dailymail.co.uk/i/pix/2012/02/17/ ar-cle- 0-11C5E3C DC- 346_468x286.jpg 17
18 hdp:// business/by- solu-on/customer- service- solu-ons/solu-ons- services/inbound- solu-ons/voice- authen-ca-on- biometrics/vocal- password/index.htm hdp:// 18
19 Digital signing Alice Bob Mallory Problem: impersona-on in public- key crypto Mallory encrypts message with Bob's public key Only Bob can decrypt using his private key Message is a love leder claiming to be from Alice 19
20 Digital signing Digital signing via public key crypto Alice encrypts message with her private key Everybody can decrypt using Alice's public key But it proves it came from Alice since no one else has her private key Encrypt result with Bob's public key Only Bob can decrypt using his private key Problem: asymmetric crypto can be expense Hash the message Encrypt just the hash 20
21 Hash- based digital signing 21
22 Distribu-ng public keys Alice has to find Bob's public key How does she know it is really Bob's key? Someone else could impersonate Bob Mallory fools Alice into using her fake Bob public key Mallory decrypts using fake Bob's private key Mallory reads message Reencrypts using Bob's real public key and sends on Problems: How do we distribute public keys? How to establish trust of keys? 22
23 PKI Public Key Infrastructure (PKI) Cer-ficate Authority (CA) Verifies user is who they say they are Digitally signs the user's public key e.g. VeriSign hdp://blog.securism.com/2009/01/summarizing- pki- cer-ficate- valida-on/ 23
24 PGP PreDy Good Privacy (PGP) 1991 Phil Zimmermann "In the past, if the Government wanted to violate the privacy of ordinary ci-zens, it had to expend a certain amount of effort to intercept and steam open and read paper mail, and listen to and possibly transcribe spoken telephone conversa-on. This is analogous to catching fish with a hook and a line, one fish at a -me. Fortunately for freedom and democracy, this kind of labor- intensive monitoring is not prac-cal on a large scale. Today, electronic mail is gradually replacing conven-onal paper mail, and is soon to be the norm for everyone, not the novelty it is today. Unlike paper mail, E mail messages are just too easy to intercept and scan for interes-ng keywords. This can be done easily, rou-nely, automa-cally, and undetectably on a grand scale. This is analogous to drihnet fishing- - making a quan-ta-ve and qualita-ve Orwellian difference to the health of democracy." - Philip Zimmermann, tesdmony to Congress 24
25 PGP PreDy Good Privacy (PGP) Focus on efficiency: RSA for symmetric key exchange Symmetric cipher (IDEA) for bulk of encryp-on Focus on ease of use: Allow average Joe to use strong cryptography User clicks to encrypt/sign an First widely available public- key crypto Released via friend to the Usenet Problems: RSA was patented by RSA Data Security, Inc. Strong encryp-on considered a muni-on by US 25
26 Key length 384 bits = casual, broken easily today 512 bits = commercial, breakable by 3- leder orgs 1024 bits = military, not breakable on earth 2048 bits = alien, unbreakable on other planets 26
27 Securing web commerce Customer fills out order with credit card # Problem 1: Keep data secure from customer's browser to the web server Problem 2: Keep data secure on server or in transit to order fulfillment 27
28 SSL Secure Sockets Layer (SSL) / Transport Layer Security (TLS) Client requests secure connec-on from server Client sends list ciphers/hash func-ons supported Server picks the strongest mutual cipher/hash Server sends back digital cer-ficate Name of itself, trusted Cer-ficate Authority (CA), public encryp-on key Client contacts CA to confirm key belongs to site Client generates session key by encryp-ng random number with server's public key Client and server con-nue using symmetric cipher 28
29 HTTPS Hypertext Transfer Protocol Secure (HTTPS) hdps:// Typically running on port
30 Proving who you are Summary Passwords, tokens, biometrics Digital signing using public key crypto Secure hash func-ons Digital signing, storage of passwords, detec-ng changes in files PGP Popular applica-on of public key crypto Secure web commerce SSL/TLS 30
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