The document summarizes the evolution of the Transport Layer Security (TLS) protocol from versions 1.0 to 1.2. It describes the key components of TLS including the record protocol for fragmenting and transmitting encrypted data, handshake protocol for authentication and key exchange, and cipher suites for encryption algorithms. The TLS protocol provides secure communication over the internet by preventing eavesdropping, tampering, and forgery of messages between client and server applications.

1. Transport Layer
Security
Mrinal Wadhwa
http://www.mrinalwadhwa.com

2. SSL v1
before 1995, internal to Netscape, never released

3. SSL v2
draft published in FEB 1995
SSL 0.2 PROTOCOL SPECIFICATION
http://www.mozilla.org/projects/security/pki/nss/ssl/draft02.html

4. SSL v3
draft published in NOV 1996
The SSL Protocol Version 3.0
http://www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt

5. TLS 1.0
RFC 2446 - in Jan 1999
The TLS Protocol Version 1.0
http://tools.ietf.org/html/rfc2246

6. TLS 1.1
RFC 4346 - in April 2006
The Transport Layer Security (TLS) Protocol Version 1.1
http://tools.ietf.org/html/rfc4346

7. TLS 1.2
RFC 5246 - in August 2008
The Transport Layer Security (TLS) Protocol Version 1.2
http://tools.ietf.org/html/rfc5246

8. "The TLS protocol provides communications security
over the Internet. The protocol allows client/server
applications to communicate in a way that is designed to
prevent eavesdropping, tampering, or message forgery."
- The Transport Layer Security (TLS) Protocol Version 1.2

9. Record Protocol
http://tools.ietf.org/html/rfc5246#section-6

10. The Record Protocol takes messages to be transmitted, fragments the
data into manageable blocks, optionally compresses the data, applies
a MAC, encrypts, and transmits the result. Received data is
decrypted, verified, decompressed, reassembled, and then delivered to
higher-level clients.

11. struct {
ConnectionEnd entity;
PRFAlgorithm prf_algorithm;
BulkCipherAlgorithm bulk_cipher_algorithm;
CipherType cipher_type;
uint8 enc_key_length;
uint8 block_length;
uint8 fixed_iv_length;
uint8 record_iv_length;
MACAlgorithm mac_algorithm;
uint8 mac_length;
uint8 mac_key_length;
CompressionMethod compression_algorithm;
opaque master_secret[48];
opaque client_random[32];
opaque server_random[32];
} SecurityParameters;

12. Change Cipher Spec
Protocol
http://tools.ietf.org/html/rfc5246#section-7.1

13. Alert Protocol
http://tools.ietf.org/html/rfc5246#section-7.2

14. Handshake Protocol
a simplified discussion
http://tools.ietf.org/html/rfc5246#section-7.3

15. Hello Request
http://tools.ietf.org/html/rfc5246#section-7.4.1.1
struct { } HelloRequest;

16. Client Hello
http://tools.ietf.org/html/rfc5246#section-7.4.1.2
struct {
ProtocolVersion client_version;
Random random;
SessionID session_id;
CipherSuite cipher_suites<2..2^16-2>;
CompressionMethod compression_methods<1..2^8-1>;
select (extensions_present) {
case false:
struct {};
case true:
Extension extensions<0..2^16-1>;
};
} ClientHello;

17. CIPHER SUITES
TLS_RSA_WITH_AES_128_CBC_SHA
"The connection is encrypted using AES_128_CBC, with SHA1 for
message authentication and RSA as the key exchange mechanism."
Mandatory Cipher Suites - http://tools.ietf.org/html/rfc5246#section-9
Cipher Suite Definitions - http://tools.ietf.org/html/rfc5246#appendix-C

18. CIPHER SUITES
TLS_RSA_WITH_AES_128_CBC_SHA
Key Exchange - RSA
Cipher - AES_128_CBC
Mac - SHA (HMAC-SHA1)

19. Server Hello
http://tools.ietf.org/html/rfc5246#section-7.4.1.3
struct {
ProtocolVersion server_version;
Random random;
SessionID session_id;
CipherSuite cipher_suite;
CompressionMethod compression_method;
select (extensions_present) {
case false:
struct {};
case true:
Extension extensions<0..2^16-1>;
};
} ServerHello;

20. Server Certificate
http://tools.ietf.org/html/rfc5246#section-7.4.2
opaque ASN.1Cert<1..2^24-1>;
struct {
ASN.1Cert certificate_list<0..2^24-1>;
} Certificate;

21. Server Hello Done
http://tools.ietf.org/html/rfc5246#section-7.4.5
struct { } ServerHelloDone;

22. Client Key Exchange Message
http://tools.ietf.org/html/rfc5246#section-7.4.7
struct {
select (KeyExchangeAlgorithm) {
case rsa:
EncryptedPreMasterSecret;
case dhe_dss:
case dhe_rsa:
case dh_dss:
case dh_rsa:
case dh_anon:
ClientDiffieHellmanPublic;
} exchange_keys;
} ClientKeyExchange;

23. Finished
http://tools.ietf.org/html/rfc5246#section-7.4.9
struct {
opaque verify_data[verify_data_length];
} Finished;

24. ?

25. - mrinalwadhwa.com
- email@mrinalwadhwa.com
- @mrinal
- github.com/mrinalwadhwa