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PV204 Security technologies
Authentication and passwords
•Petr Švenda svenda@fi.muni.cz
•Faculty of Informatics, Masaryk University

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How to approach homework I.
•What you should listed about your configuration (replication)
–live vs. dedicated machine ® impact on measurement
–list platform configuration, compilation flags used (for replication)
•Analysis
–good to print only shape of histogram instead of bars (visibility)
–good to print multiple histograms in single graph - better visibility
–don't compare only non-blinded to blinded version. More sense makes to compare different
data/exponent for given version (e.g., blinded)
•Good to test also with medium hamming weight
–more spread in histogram with same data ® harder to use Template attacks
–but be aware what is included in timing - e.g., generation of masking r? Network jitter (attacker
can model and subtract)?
•
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PV204 Authentication and passwords

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Example solution (O. Mosnacek)
3
PV204 Authentication and passwords

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Conclusions for Homework I.
•Variability for same data and key => noise in measurement (=> potentially harder to attack)
•Difference between any two measured values => possibility to use template attack
•Difference between data with low/mid/high hamming weight => some information is leaking
•Dependency of time on HW of private exponent may be possible to detect even for blinded RSA
•
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PV204 Authentication and passwords

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AUTHENTICATION & AUTHORIZATION
•
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PV204 Authentication and passwords

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Basic terms
•Identification
–Establish what the (previously unknown) entity is
•Authentication
–Verify if entity is really what it claims to be
•Authorization (access control)
–Define an access policy to use specified resource
–Check if entity is allowed (authorized) to use resource
•Authentication may be required before entity allowed to use resource to which is authorized
PV204 Authentication and passwords
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Hierarchy of authentication and
key establishment goals
PV204 Authentication and passwords
D:\Documents\Obrazky\keystablish_goals.png
Protocols for Authentication and Key Establishment By Colin Boyd, Anish Mathuria
7

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PASSWORDS
•
PV204 Authentication and passwords
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Mode of usage for passwords
1.Verify by direct match
–provided_password == expected_password?
–Example: HTTP basic access authentication
–Be aware of potential side-channels
2.Verify by derived value (hash(password))
–Be aware of rainbow tables and brute-force crackers
3.Derive key: Password ® cryptographic key
–Example: key = PBKDF2(password)
4.Use to establish authenticated key
–Example: Password + Diffie-Hellman ® authenticated key
•…
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PV204 Authentication and passwords

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Problems associated with passwords
•How to create strong password?
•How to use password securely?
•How to store password securely?
•Same value is used for the long time (exposure)
•Value of password is independent from target operation (e.g., authorization of request)
•…
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PV204 Authentication and passwords

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Where passwords can be compromised?
1.Database storage
–Cleartext storage
–Backup data (tapes)
–Server compromise
2.Host machine (memory, history, cache)
3.Network transmission (network sniffer, proxy logs)
4.Hardcoded secrets (inside app binary)
–Difficult to change after exposure
PV204 Authentication and passwords
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Password (hash) cracking
•Scenario: dump of passwords hash database
•Password cracking attacks
–Brute-force attack (up to 7-8 characters)
–Dictionary attack (inputs with higher probability)
–Dictionary + brute-force (Password[0-9]*)
–Rainbow tables (time-memory trade-off)
–Parallelization (many parallel cores)
–GPU/FPGA/ASIC speedup of cracking
•Tools
–Generic: John the Ripper, Brutus, RainbowCrack…
–Targeted to application: TrueCrack, Aircrack-NG…
PV204 Authentication and passwords
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Password cracking defenses
•Don’t transmit or store in plaintext
•Process password on client, transmit only digest
•Don’t encrypt, hash instead
•Use salt to prevent rainbow tables attack
•Use memory-hard KDF algorithms
–To slow down custom build hardware
–Use strong KDF to derive keys (PBKDF2®Argon2)
–
•
PV204 Authentication and passwords
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Handling passwords in source code
•Limiting memory exposure
–Load only when needed
–Erase right after use
–Pass by reference / pointer to prevent copy in memory
–Derive session keys
•Don’t hardcode password into application binary
•Nice presentation (K. Kohli, examples how not to):
http://www.slideshare.net/amiable_indian/insecure-implementation-of-security-best-practices-of-hash
ing-captchas-and-caching-presentation
•
–
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Hard-coded password might be visible both in application binary and memory
| PV204: Reverse engineering of binary applications

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Alternative to hardcoded passwords/keys
•Don’t use passwords J
•Ask the user for a password
•Keep secrets in a separate file
•Encrypt stored secrets
•Store secrets in protected database
•Use already existing authentication credentials
•Cern guidelines
–https://security.web.cern.ch/security/recommendations/en/password_alternatives.shtml
–
•
PV204 Authentication and passwords
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Possible password replacements
•Cambridge’s TR – wide range of possibilities listed
–The quest to replace passwords: a framework for comparative evaluation of Web authentication
schemes
–https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-817.pdf
•Many different possibilities, but passwords are cheap to start with, lot of legacy code exists and
no mechanism offers all benefits
•Mandatory reading: UCAM-CL-817
–At least chapters: II. Benefits, V. Discussion
–Whole report is highly recommended
–
•
PV204 Authentication and passwords
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ONE-TIME PASSWORDS
•
PV204 Authentication and passwords
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Recall: Problems associated with passwords
•How to create secure password?
•How to use password securely?
•How to store password securely?
•Same value is used for the long time (exposure)
•Value of password is independent from target operation (e.g., authorization of request)
•…
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PV204 Authentication and passwords
One-time passwords tries to address these issues

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HMAC-based One-time Password Algorithm
•HMAC-based One-time Password Algorithm (HOTP)
–Secret key K
–Counter (challenge) C
–HMAC(K,C) = SHA1(K ⊕ 0x5c5c… ∥ SHA1(K ⊕ 0x3636… ∥ C))
–HOTP(K,C) = Truncate(HMAC(K,C)) & 0x7FFFFFFF
–0x7FFFFFFF mask to drop most significant bit (portability)
–HOTP-Value = HOTP(K,C) mod 10d     (d … # of digits)
•Many practical implementations
–E.g., Google authenticator
•https://en.wikipedia.org/wiki/HOTP
•
PV204 Authentication and passwords
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HOTP – items, operations
•Logical operations
1.Generate initial state for new user and distribute key
2.Generate HOTP code and update state (user)
3.Verify HOTP code and update state (auth. server)
•Security considerations of HOTP
–Client compromise
–Server compromise
–Repeat of counter/challenge
–Counter mismatch tolerance window
•
•
•
PV204 Authentication and passwords
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Sylvain Maret
Time-based One-time Password Algorithm
•Very similar to HOTP
–Time used instead of counter
•Requires synchronized clocks
–In practice realized as time window
•Tolerance to gradual desynchronization possible
–Server keeps device’s desynchronization offset
–Updates with every successful login
PV204 Authentication and passwords
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OCRA: OATH Challenge-Response Algorithm
•Initiative for Open Authentication (OATH)
•OCRA is authentication algorithm based on HOTP
•OCRA code = CryptoFunction(K, DataInput)
–K: a shared secret key known to both parties
–DataInput: concatenation of the various input data values
•Counter, challenges, H(PIN/Passwd), session info, H(time)
–Default CryptoFunction is HOTP-SHA1-6
–https://tools.ietf.org/html/rfc6287
•Don’t confuse with OAuth
–The OAuth 2.0 Authorization Framework (RFC6749)
–TLS-based security protocol for accessing HTTP service
PV204 Authentication and passwords
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Increased risk at *OTP verification server
•More secure against client compromise
–Using OTP instead of passwords, KDF(time|key),
•But what if server is compromised?
–database hacks, temporal attacker presence
–E.g., Heartbleed – dump of OTP keys
•Possible solution
–Trusted hardware on the server
–OTP code verified inside trusted environment
–OTP key never leaves the hardware
PV204 Authentication and passwords
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METHODS OF DERIVATION OF SECRETS FROM PASSWORD
•
PV204 Authentication and passwords
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D:\Documents\Obrázky\is2\Key-icon.png
H(‘Password’) ®

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Problems when password used as a key
•Passwords are usually shorter / longer than key
•If password as a key => low number of distinct keys
•Password does not contain same amount of entropy as binary key (only printable characters…)
•K = SHA-2(“password”)
–Same passwords from multiple users => same key
–Large pre-computed “rainbow” tables allow for quick check
–Solved by addition of random (potentially public) salt
•K = SHA-2(pass | salt)
•Dictionary-based brute-force still possible
•
PV204 Authentication and passwords
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D:\Documents\Obrazky\pbkdf2-5002.png
Derivation of secrets from password
•PBKDF2 function, widely used
–Password is HMAC “key”
–Iterations to slow derivation
–Salt added
•
•
•
•Problem with custom-build hardware (GPU, ASIC)
–Repeated iterations not enough to prevent bruteforce
–(or would be too slow on standard CPU – user experience)
•
PV204 Authentication and passwords
Source: https://nakedsecurity.sophos.com
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scrypt – memory hard function
•Design as a protection against cracking hardware (usable against PBKDF2)
–GPU, FPGA, ASICs…
–https://github.com/wg/scrypt/blob/master/src/main/java/com/lambdaworks/crypto/SCrypt.java
•Memory-hard function
–Force computation to hold r (parameter) blocks in memory
–Uses PBKDF2 as outer interface
•Improved version: NeoScrypt (uses full Salsa20)
•
PV204 Authentication and passwords
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Reuse of external PBKDF2 structure
PV204 Authentication and passwords
https://www.reddit.com/r/crypto/comments/3dz285/password_hashing_competition_phc_has_selected/
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Argon2
•Password hashing competition (PHC) winner, 2013
•
•
PV204 Authentication and passwords
https://www.reddit.com/r/crypto/comments/3dz285/password_hashing_competition_phc_has_selected/
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Problem solved?
•
33
I PA193 - Secure channel, storage and envelope
https://www.ietf.org/mail-archive/web/cfrg/current/msg08439.html

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PASSWORD MANAGERS
•
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PV204 Authentication and passwords

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Evolution of password (managers)
1.Human memory only
2.
2.Write it down on paper
3.
3.Write it into file
4.
4.Use local password manager
5.
5.
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PV204 Authentication and passwords
D:\Documents\Obrázky\is2\Body-Brain-icon.png
Pαs$w0rd
Pαs$w0rd01
Google:
Sfdlk2c&
Skype:
*(&21mefd
D:\Documents\Obrázky\is2\NotepadRv1.png devil
Google:
Sfdlk2c&432mo%
Skype:
*(&21mefd872!&
Google:
Sfdlk2c&432mo%
Skype:
*(&21mefd872!&
devil D:\Documents\Obrázky\is2\Key-icon.png D:\Documents\Obrazky\is2\synchronization.png

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D:\Documents\Obrázky\is2\Plain-Blue-icon.png
Remote password managers
Google:
Sfdlk2c&432mo%
Skype:
*(&21mefd872!&
D:\Documents\Obrázky\is2\Lock-icon.png D:\Documents\Obrázky\is2\Phone-icon.png
D:\Documents\Obrázky\is2\ipad-black-icon.png D:\Documents\Obrázky\is2\Computer_Icon.png
D:\Documents\Obrázky\is2\Key-icon.png D:\Documents\Obrázky\is2\Key-icon.png
D:\Documents\Obrázky\is2\Key-icon.png
KeePass+Dropbox
LastPass
1Password
MozillaSync
…
PV204 Authentication and passwords
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•
D:\Documents\Obrázky\is2\lastpasshack.png >
But passwords are encrypted, right?
D:\Documents\Obrázky\is2\lastpass_usersshouldbesafe.png
PV204 Authentication and passwords
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D:\Documents\Obrázky\is2\Plain-Blue-icon.png
D:\Documents\Obrázky\is2\Places-server-database-icon.png
Human is still the weakest link
Google:
Sfdlk2c&432mo%
Skype:
*(&21mefd872!&
D:\Documents\Obrázky\is2\Lock-icon.png D:\Documents\Obrázky\is2\Computer_Icon.png >
More than 60% of users have weak passwords
D:\Documents\Obrázky\is2\Body-Brain-icon.png D:\Documents\Obrázky\is2\Key-icon.png
D:\Documents\Obrázky\is2\Key-icon.png devil
D:\Documents\Obrázky\is2\Places-server-database-icon.png D:\Documents\Obrázky\is2\Lock-icon.png
D:\Documents\Obrázky\is2\Plain-Blue-icon.png
password123
Google:
Sfdlk2c&432mo%
Skype:
*(&21mefd872!&
D:\Documents\Obrázky\is2\johntheripper1_10_design.png
PV204 Authentication and passwords
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Hardware tokens
•
D:\Documents\Obrázky\is2\gcr-smart-card.png D:\Documents\Obrázky\is2\multipass.JPG
D:\Documents\Obrázky\is2\passwordlockusb2.jpg
Hack-a-Day’s Mooltipass
>
Price, usability, compatibility…
PV204 Authentication and passwords
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Common (mis-)Assumptions
1.User has strong password
2.Server/service is hard to compromise
3.User have unique passwords
4.Different authentication channels are independent
5.Recovery
6.
6.
6.
6.
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PV204 Authentication and passwords

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D:\Documents\Obrázky\is2\linkedin_hack.png
•
>
User has strong password
D:\Documents\Obrázky\is2\linkedin_badpasswd.png
PV204 Authentication and passwords
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D:\Documents\Obrázky\is2\passwod_reuse.png
D:\Documents\Obrázky\is2\infoworld_passwordreuse.png >
Study: Gawker vs. root.com passwords leak
“…[from successfully cracked passwords] 76% used the exact same password. A further 6% used
passwords differing by only capitalisation or a small suffix (e.g. ‘password’ and ‘password1′).”,
J. Bonneau
http://www.lightbluetouchpaper.org/2011/02/09/measuring-password-re-use-empirically/
>
User have unique passwords…
PV204 Authentication and passwords
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•
D:\Documents\Obrázky\is2\password breaches.png D:\Documents\Obrázky\is2\password breaches.png
D:\Documents\Obrázky\is2\password breaches.png >
Service is hard to compromise?
PV204 Authentication and passwords
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•
>
Services follow the best security principles
D:\Documents\Obrázky\is2\starbucks_plaintextpass.png >
Service implementation is correct and bug-free
D:\Documents\Obrázky\is2\Heartbleed.svg.png
PV204 Authentication and passwords
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•
•
>
Different authentication channels are independent
D:\Documents\Obrázky\is2\Computer_Icon.png D:\Documents\Obrázky\is2\Backup-IBM-Server-icon.png
D:\Documents\Obrázky\is2\nokia_7.jpg D:\Documents\Obrázky\is2\Apps-firefox-icon.png
D:\Documents\Obrázky\is2\SMS-icon.png D:\Documents\Obrázky\is2\iPhone-icon.png
D:\Documents\Obrázky\is2\Apps-firefox-icon.png D:\Documents\Obrázky\is2\Mail-icon.png
D:\Documents\Obrázky\is2\SMS-icon.png
PV204 Authentication and passwords
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•
•
•
•
>
Security can be maintained “forever”
D:\Documents\Obrázky\is2\basket-empty-icon.png >
Allow for some form of risk management
D:\Documents\Obrázky\is2\Key-icon3.png D:\Documents\Obrázky\is2\System-Key-icon.png
D:\Documents\Obrázky\is2\key-icon2.png D:\Documents\Obrázky\is2\Key-icon.png
PV204 Authentication and passwords
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D:\Documents\Obrázky\is2\mothermaidens.png
•
D:\Documents\Obrázky\is2\questions_guess.png D:\Documents\Obrázky\is2\lost_N_twitter.png >
Recovery info shared over multiple services…
>
PV204 Authentication and passwords
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Access recovery is as secure as primary one

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PASSWORD MANAGER FOR MULTIPLE DEVICES
•Case study
PV204 Authentication and passwords
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Assumptions
•Functional
–User stores fixed secrets (passwords…)
–User has multiple connected devices
–Easy to use J
•Security
–Service can’t be trusted
–User chooses weak password
–Devices can be lost (and later revoked)
–User has independent channel (phone)
•
•
PV204 Authentication and passwords
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Main security design principles
•Treat storage service as untrusted and perform security sensitive operations on client
•Make necessary trusted component as small as possible
•Prevent offline brute-force, but don’t expect strong password from user
–add entropy from other source
•Make transmitted sensitive values short-lived
•Trusted hardware can provide additional support
–
PV204 Authentication and passwords
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Public-key cryptography indirection
D:\Documents\Obrázky\is2\Plain-Blue-icon.png
Google:
Sfdlk2c&432mo%
Skype:
*(&21mefd872!&
D:\Documents\Obrázky\is2\Lock-icon.png D:\Documents\Obrázky\is2\Computer_Icon.png
D:\Documents\Obrázky\is2\Body-Brain-icon.png D:\Documents\Obrázky\is2\Key-icon.png
K = H(‘Password’)
K
D:\Documents\Obrázky\is2\Plain-Blue-icon.png
Google:
Sfdlk2c&432mo%
K
Password
  Priv_U
KEK
  K
Pub_U
D:\Documents\Obrázky\is2\Computer_Icon.png D:\Documents\Obrázky\is2\Body-Brain-icon.png
D:\Documents\Obrázky\is2\Key-icon.png
Password
KEK = H(‘Password’)
PV204 Authentication and passwords
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D:\Documents\Obrázky\is2\Computer_Icon.png D:\Documents\Obrázky\is2\ipad-black-icon.png
D:\Documents\Obrázky\is2\Phone-icon.png >
Public-key crypto indirection
D:\Documents\Obrázky\is2\Plain-Blue-icon.png
Google:
Sfdlk2c&432mo%
K
  Priv_U
KEK
  K
Pub_U
D:\Documents\Obrázky\is2\Computer_Icon.png D:\Documents\Obrázky\is2\Key-icon.png
Password
KEK = H(‘Password’)
>
Public-key crypto indirection allows for asynchronous change of K
>
Long private key can be also stored on Service
D:\Documents\Obrázky\is2\User-Group-icon.png
K’,K’’,K’’’…
[K’]Pub_U
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg >
Weak password?
D:\Documents\Obrázky\is2\Plain-Blue-icon.png D:\Documents\Obrázky\is2\Plain-Blue-icon.png
•
Google:
Sfdlk2c&432mo%
K
  Priv_U
KEK
  K
Pub_U
D:\Documents\Obrázky\is2\Computer_Icon.png D:\Documents\Obrázky\is2\Key-icon.png
Password
KEK = H(‘Password’)
Password
KEK = H(‘Password’)
KEK
Priv_U
K
K
Google:
Sfdlk2c&432mo%
>
Attacker has motivation for attacking the Service!
>
Users tend to have weak passwords…
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg
D:\Documents\Obrázky\is2\Home-Server-icon.png D:\Documents\Obrázky\is2\Home-Server-icon.png >
Trusted element
•
D:\Documents\Obrázky\is2\Plain-Blue-icon.png
Google:
Sfdlk2c&432mo%
K
  Priv_U
KEK
  K
Pub_U
D:\Documents\Obrázky\is2\Computer_Icon.png D:\Documents\Obrázky\is2\Body-Brain-icon.png
D:\Documents\Obrázky\is2\Key-icon.png
Password
KEK = H(‘Password’
D:\Documents\Obrázky\is2\Home-Server-icon.png
User1:SecretData
User2:SecretData’
…
>
Separate trusted entities provide additional data
| SecretData)
devil
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg
•
D:\Documents\Obrázky\is2\Plain-Blue-icon.png
Google:
Sfdlk2c&432mo%
K
  Priv_U
KEK
  K
Pub_U
D:\Documents\Obrázky\is2\Computer_Icon.png D:\Documents\Obrázky\is2\Body-Brain-icon.png
D:\Documents\Obrázky\is2\Key-icon.png
Password
KEK = H(‘Password’ | SecretData)
D:\Documents\Obrázky\is2\Home-Server-icon.png
User1:SecretData
User2:SecretData’
…
D:\Documents\Obrázky\is2\nokia_7.jpg
SMS:
D:\Documents\Obrázky\is2\Key-icon.png
SecretData
D:\Documents\Obrázky\is2\Key-icon.png
SecretData
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg >
Multiple devices
•
D:\Documents\Obrázky\is2\Plain-Blue-icon.png
Google:
Sfdlk2c&432mo%
K
  Priv_U
KEK
  K
Pub_U
KEK
Dev1
KEK
Dev2
KEK
Dev3
D:\Documents\Obrázky\is2\Phone-icon.png D:\Documents\Obrázky\is2\ipad-black-icon.png
D:\Documents\Obrázky\is2\Computer_Icon.png
Dev1
Dev2
Dev3
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg
•
•Device management (new, remove, revoke)
•Device authentication
•Group management (users, boards, secrets)
•Password change, private key change
•Access recovery
•…
>
Devil is in the details…
>
Other operations
devil
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg
Do we have some implementations?
•
•Apple’s service showcased in 2013
•Lack of details until iOS Security report 02/2014
–https://www.apple.com/business/docs/iOS_Security_Guide.pdf
–
•
D:\Documents\Obrázky\is2\24591_icloud-keychain-660x350.jpg
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg
 Apple’s iCloud Keychain
•Multiple similarities to described example
–Layer of indirection via asymmetric cryptography
–Support for multiple devices
–Asynchronous operations via application tickets
–Authorization and signature of additional devices
–User phone registered and required
•Still reliance on user’s (potentially weak) password
–But limited number of tries (recall recent FBI 10 password attempts)
•Trusted component of iCloud realized via internal HSM
–Recovery mode with 4 digit code (default, can be set longer)
–HSM will decrypt recovery key only after code validation
–4 digits length is not an issue here – HSM enforce limited # retries
PV204 Authentication and passwords
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P:\CRCS\2012_0178_Redesign_loga_a_JVS\PPT_prezentace\sablona\pracovni\normalni.jpg
Summary
•Passwords have multiple issues, but are hard to be replaced
•Important to use passwords securely (guidelines)
•One-time passwords getting more used
•Password manager with synchronization over multiple devices is not straightforward
•Mandatory reading: UCAM-CL-817
–At least chapters: II. Benefits, V. Discussion
–Whole report is highly recommended
•
•
•
•
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