We need to protect our Internet communication - from basic web surfing to IP telephony, E-mail and Internet of things. This presentation gives some background and introduces one of the core security protocols - TLS, Transport Layer Security. This presentation is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. Update: See http://www.slideshare.net/oej/morecrypto-with-tis-version-20

1. #MoreCrypto
A small step to make it harder
to listen to IP based activity.
V1.8 TLS - oej@edvina.net - slideshare.net/oej
Ⓒ Olle E. Johansson, Stockholm, Sweden 2014.
This work is licensed under
2014-02-09

2. The problem
We have built an information network
that is too easy to monitor. We simply
trusted everyone too much in a naive way.
Sadly, we can’t do
that any more.

3. The Internet mirrors society
When the Internet was small, there was a select group
of people using it. They felt is was a safe place.
#MoreCrypto

4. As the Internet grew and reflects more of society,
we forgot to harden it. It’s time now.
#MoreCrypto

5. The engineers are working
The IETF is the organisation that defined
most of the standards we use today to
The IETF recently decided to focus a lot of
energy to add more confidentiality and
security in general to the technology
we use every day.
communicate.
#MoreCrypto

6. What’s the problem?

7. Changing the Internet
is too hard.
We are not using the
security tools we have in the
way they are meant to be
used today. In some cases, like e-mail and
IP telephony, most of us do not
use any security tools at all.
#MoreCrypto

8. How do we change?
The users must require change. Otherwise,
very few things happen. It is up to you and me.
#MoreCrypto

9. What needs to be done?
More crypto Easy to use authentication
Enhanced privacy Stronger confidentiality
A lot of changes needs to be done in how we build
services, operate them and use them.
#MoreCrypto
…and much more

10. TLS is an important tool
#MoreCrypto
TLS
Transport
Layer
Security
TLS provides confidentiality, identity
and integrity to Internet communication.
TLS is used in HTTPS:// web pages, but can also be
used from applications on a computer as well as a cell
phone.
TLS is based on SSL, that was a provider-specific
technology. TLS is maintained by the IETF and is still
being improved.
The second part
covers this!

11. Start simple.
Use connection encryption
wherever possible.
Use HTTPS and serve
information over HTTPS
#MoreCrypto
In short:
#MoreCrypto

12. Why?
More crypto on the Internet
raise the cost of listening in to
our information flows, our
conversations. It does not solve all the issues,
we have a lot of work
#MoreCrypto
ahead of us.
Using more TLS is not very
complicated and can be used in
most applications today.

13. Starting points.
Enable HTTPS for Facebook,
Google and other services
when you can.
Use EFF HTTPS ANYWHERE
in your web browser.
If you are a sysadmin, enable
TLS and follow new advice on
choice of algorithms.
#MoreCrypto

14. What does TLS give you?
Browser Confidential path Server
Other people in the same network (or IT management)
can see where you go (server address), but not what you do.
#MoreCrypto
Example:
Hotel staff can’t see what you write
or read on Facebook.

15. What about VPN tunnelling?
Computer Confidential path
Example: Other people in the same
network (or IT management)
can see that you are using a VPN,
VPN
server
#MoreCrypto
but not what you do.
Web
Server
Mail
Server
VPN = Virtual private network
On the other side of the VPN
server your connections become
visible again - unless you are using TLS.
Example:
Hotel staff can’t see which web
sites you are connecting to.

16. The work continues
#MoreCrypto
Mobile
apps
Web
IP
Telephony
E-mail
Cloud
Services
Internet of
things
The Digital
home
Chat
Video
Services
Require
#MoreCrypto!

17. NEW!
OPPURTUNISTIC
SECURITY
Secure network traffic, regardless of what the user says.
Do whatever you can to make it harder to listen in.

18. Introduction to TLS
Transport Layer Security
#MoreCrypto

19. Security basics.
#MoreCrypto
Identity
Confidentiality
Authorization
Integrity
Non-repudiation

20. TLS is an important tool
#MoreCrypto
TLS
Transport
Layer
Security
TLS provides confidentiality, identity
and integrity to Internet communication.
TLS is used in HTTPS:// web pages, but can also be
used from applications on a computer as well as a cell
phone.
TLS is based on SSL, that was a provider-specific
technology. TLS is maintained by the IETF and is still
being improved.

21. Encryption
SYMMETRIC ASYMMETRIC
Using the same key for
encryption and decryption
Using the different keys for
encryption and decryption
Simple for the CPU,
supports streaming data
More computations,
easier for data blocks
#MoreCrypto

22. Using a private
and a public key
• TLS use a keypair to set up a secure connection
• Assymetric encryption
• The server sends the public key at connection
• The client challenges the server
• The server responds to the challenge using the
server private key
• Now the client knows that the server has the
private key that matches the public key
private

23. TLS Usage
• TLS is used for
• authentication of servers and
clients
• initiating encryption of a session
• digital signatures on messages to
ensure integrity and provide
authentication
Authentication
Who are you? Prove it!
Encryption
Providing confidentiality
Integrity
Making sure that the
receiver get what the
sender sent

24. Adding a certificate
to the mix
• A certificate is nothing more complicated than a
passport or an ID card
• It contains the public key and some administrative
data
• And is signed (electronically) by someone you
might trust ... or not.
• This is part of the complex structure called PKI,
which you might want or just disregard
• A PKI is not needed to get encryption for the
signalling path!
• You can however use a PKI to only set up
connections that you trust

25. The X.509v3 certificate
• An X.509 certificate is the standardised way to
bind a public key to an identity
• The certificate is issued by a
Certification Authority (CA)
• The most important component of the PKI?
• An X.509 certificate is an
electronic document with a specific layout
!
• Standard: documented in IETF PKIX RFC:s
Version
Serial number
Issuer identity
Validity period
User identity
Public key
Extension fields

26. X509.v3
contents
• Version number
• Certificate serial number
Used for validation
• Identity of the issuer
• Validity period
• Identity of the public key owner
• Public key
• Extension fields
• A digital signature, created by the issuer
Internet
Explorer
Certificate
Manager

27. Example: SIP certificates
• SubjectAltName contains a list of
identities that are valid for this
certificate
• RFC 5922 outlines a SIP event package
to distribute and manage certificates
• This is based on the Authentication
Service in SIP identity (RFC 4474)
• The domain cert is used to sign the
NOTIFY payload
TLS is more than the
world wide web!

28. x.509 cert for SIP
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
01:08:00:79:00:15:00:43
Signature Algorithm: sha1WithRSAEncryption
Issuer: C=US, ST=California, L=San Jose, O=sipit, OU=Sipit Test Certificate Authority
Validity
Not Before: Sep 16 17:17:00 2009 GMT
Not After : Sep 15 17:17:00 2012 GMT
Subject: C=US, ST=California, L=San Jose, O=sipit, CN=tls6.test.sipit.net
Subject Public Key Info:
Public Key Algorithm: rsaEncryption
RSA Public Key: (2048 bit)
Modulus (2048 bit):
00:a7:96:65:6e:b6:ba:3a:48:a1:bd:a3:ae:21:dc:
a8:92:97:3c:43:ea:24:e6:9f:93:2f:61:7e:d3:2d:
30:1e:21:42:b9:d6:59:87:f1:b1:f8:c8:39:8e:43:
64:9a:31:2c:18:3d:cd:d8:03:64:bb:14:38:44:05:
20:30:d8:e1:db:a7:4d:c3:47:a2:49:73:d1:10:ed:
2f:cf:74:26:57:91:64:af:b0:f2:5d:3f:88:9f:df:
65:6c:ba:65:3f:66:99:52:6b:20:d2:0e:e3:65:18:
b1:8e:3d:ca:f2:4a:45:c5:4d:85:ef:82:54:f8:54:
54:db:96:90:9b:c5:1b:2a:1e:60:3c:43:71:55:60:
30:93:8f:fd:d8:d9:3d:a1:32:e3:56:4b:e2:73:b6:
cc:18:93:8a:d8:8b:68:81:c7:fd:cd:d5:dc:4c:a2:
86:61:9f:ad:d0:b1:d3:3c:4c:6c:07:54:b2:43:b4:
a7:0a:0a:f2:e3:6d:12:43:16:70:63:c9:e9:1a:78:
66:9d:ee:30:94:7b:ab:f2:e9:67:4a:66:6d:8c:ed:
a8:a4:98:51:77:0b:a7:60:55:73:85:87:4a:57:6b:
24:fe:27:00:02:79:70:da:5a:45:ad:aa:3d:d5:40:
5b:5c:85:63:93:56:af:c7:e8:e3:b6:1a:25:b6:a2:
2d:37
Exponent: 65537 (0x10001)
X509v3 extensions:
X509v3 Subject Alternative Name:
DNS:test.sipit.net, DNS:tls6.test.sipit.net, URI:sip:tls6.test.sipit.net
X509v3 Basic Constraints:
CA:FALSE
X509v3 Subject Key Identifier:
27:F7:A9:96:F5:B2:8F:0B:5E:A9:C7:F5:0F:AC:3D:AB:3D:8D:F0:30
Signature Algorithm: sha1WithRSAEncryption
1a:fe:1f:af:86:99:82:e5:14:97:8d:64:9a:d1:5c:ea:6c:96:
f5:c6:0c:7d:20:5f:4e:70:05:24:3a:de:b5:b9:cf:66:8d:4c:
74:d5:6a:a9:52:74:17:bc:b4:79:a0:58:32:78:a9:70:7c:6a:
15:ac:07:29:77:13:06:55:53:3f:0b:4c:3d:da:55:6e:ad:74:
56:01:55:c8:4c:19:8d:06:0b:f3:4c:04:d5:9a:6f:44:ad:7a:
fd:3b:aa:e8:4b:84:6e:f1:c4:34:f4:a0:6a:f6:81:ae:74:b4:
46:6e:b9:2f:a6:59:f1:02:e9:58:7c:a1:8d:08:31:2b:39:ee:
eb:7e
Subject: C=US, ST=California, L=San Jose, O=sipit, CN=tls6.test.sipit.net
X509v3 Subject Alternative Name:
DNS:test.sipit.net, DNS:tls6.test.sipit.net, URI:sip:tls6.test.sipit.net
Notice the URI in the certificate!

29. Process for a server
Generate
Keys
Pack public key
in CSR
Send CSR
to CA
CA validate
process
CA issues
Certificate
Install cert
in server with
private key

30. Client connection
Open TCP
connection
Server sends
certificate
Client
challenge server
Server answers
challenge
Client validates
certificate
Server can issue
cert request
Client and server
produce session key
Symmetric encryption
starts

31. Issues
Certificate can validate correctly
with the CA store, but still be the
wrong certificate.
Certificate private key can be
copied and certificate
revocated.
DNS was spoofed, so we
reached the wrong service
Something new and even more
scary than Heartbleed.

32. Protocol specifics
• Given a protocol request - how do we match the
request address to a certificate
• SIP Uri, E-mail address, HTTPS uri

33. TLS and SSL
SSL v1.0 - 2.0
Created by Netscape
Communications
Deemed insecure.
SSL v3.0
Last version. No support for
extensions and not for modern
crypto algorithms. Deemed
insecure.
#MoreCrypto
TLS 1.x
Open standard defined by the
IETF. Keeps being updated.
It’s time to try to stop
using SSL.

34. Man in the middle
Client MITM Server
• How do we prevent and discover TLS proxys?
• Quite commonly used

35. Certificate Fingerprinting
Certificates have a fingerprint, a
checksum of the cert and key.
Embed last, current and next
certificate fingerprint in the code
Verify that you are talking with
the expected server.
TLS verification may work with a
bad server cert too.
Client Server
Client MITM Server
#MoreCrypto

36. Trust on first use
Save certificate fingerprint on
first connection
If another certificate shows up,
warn the user
Don’t block, the first connection
could be bad
Certificates gets updates
so save expiry time and
accept new.
Client Server
Client MITM Server
#MoreCrypto

37. DANE - using DNSsec
Save cert in DNS, signed by
Client DNS
DNS query
Client Server
#MoreCrypto
DNSsec
If another certificate shows up,
do not continue. Disconnect.
Certificates that expired or was
revoked has no NS records
TLS connection
Client MITM Server

38. User specifics
• Which CAs do we trust?
• How do we check validity of certificate, even if
we trust the CA?
• Do we have time for validation?

39. New solutions
• Anchoring the certificate in DNS
• Validating the certificate in DNS
• No certificate - bare keys
• Oppurtunistic Security with TLS
DNSsec

40. Advice:
• Use encrypted communication by default
• Authenticated sessions are better than non-authenticated
• If you really need confidentiality, check ciphers
and checksum algorithms
#MoreCrypto

41. Heartbleed
• Programming error in OpenSSL
• OpenSSL is used in too many
places
• Opened up for private key
distribution and a lot of other
in-memory data.

42. Security is a process
• There will be other issues with
TLS libraries, protocols and
implementations
• Having these is better than
having no security, integrity,
privacy or confidentiality

43. To-do list
Always build secure platforms. Encrypt all communication. 1.
Integrate IPv6 in every single project. 2.
Sign your DNS data. DNS is the foundation for all of Internet. 3.
#MoreCrypto
SECURITY:
IPv6:
DNSsec:

44. The way forward:
#MoreCrypto

45. More information
http://www.internetsociety.org/deploy360/tls/
https://bettercrypto.org
http://tools.ietf.org/html/rfc7258 - Internet is under attack.
#MoreCrypto

46. Join us!
• IETF peerpass mailing list, UTA working group
and more.
• Hashtag #MoreCrypto
• http://internetsociety.org

47. #MoreCrypto
Feedback?
• Feedback and suggestions for improvements to this presentation is
more than welcome! Send to oej@edvina.net!
• Feel free to use this presentation yourself - Notice the Creative
commons license on this presentation!
• Please tell me if you use it! It’s always fun to know.
Olle E. Johansson
Author: oej@edvina.net - slideshare.net/oej
Ⓒ Olle E. Johansson, Stockholm, Sweden 2014.
This work is licensed under