Differences between SSL and TLS Protocol Versions

Have you heard talk about SSL 3.0, TLS 1.0, TLS 1.1, and TLS 1.2 but never really knew the differences between the different versions? Secure Socket Layer (SSL) and Transport Security Layer (TLS) are both cryptographic protocols which provide secure communication over networks. These different versions are all in widespread use today in applications such as web browsing, e-mail, instant messaging and VoIP, and each is slightly different from the others.

wolfSSL supports all three of these ciphers to best suit your needs and requirements. wolfSSL and GnuTLS are the only two SSL/TLS libraries which support TLS 1.2. Below you will find the major differences between the different protocol versions.

SSL 3.0
This protocol was released in 1996, but first began with the creation of SSL 1.0 developed by Netscape. Version 1.0 wasn`t released, and version 2.0 had a number of security flaws, thus leading to the release of SSL 3.0. Some major improvements of SSL 3.0 over SSL 2.0 are:
– Separation of the transport of data from the message layer
– Use of a full 128 bits of keying material even when using the Export cipher
– Ability of the client and server to send chains of certificates, thus allowing organizations to use certificate hierarchy which is more than two certificates deep.
– Implementing a generalized key exchange protocol, allowing Diffie-Hellman and Fortezza key exchanges as well as non-RSA certificates.
– Allowing for record compression and decompression
– Ability to fall back to SSL 2.0 when a 2.0 client is encountered

Netscape`s Original SSL 3.0 Draft: http://www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt
Comparison of SSLv2 and SSLv3: http://stason.org/TULARC/security/ssl-talk/4-11-What-is-the-difference-between-SSL-2-0-and-3-0.html

TLS 1.0
This protocol was first defined in RFC 2246 in January of 1999. This was an upgrade from SSL 3.0 and the differences were not dramatic, but they are significant enough that SSL 3.0 and TLS 1.0 don`t interoperate. Some of the major differences between SSL 3.0 and TLS 1.0 are:
– Key derivation functions are different
– MACs are different – SSL 3.0 uses a modification of an early HMAC while TLS 1.0 uses HMAC.
– The Finished messages are different
– TLS has more alerts
– TLS requires DSS/DH support

RFC 2246: http://tools.ietf.org/html/rfc2246

TLS 1.1
This protocol was defined in RFC 4346 in April of 2006, and is an update to TLS 1.0. The major changes are:
– The Implicit Initialization Vector (IV) is replaced with an explicit IV to protect against Cipher block chaining (CBC) attacks.
– Handling of padded errors is changed to use the bad_record_mac alert rather than the decryption_failed alert to protect against CBC attacks.
– IANA registries are defined for protocol parameters
– Premature closes no longer cause a session to be non-resumable.

RFC 4346: http://tools.ietf.org/html/rfc4346#section-1.1

TLS 1.2
This protocol was defined in RFC 5246 in August of 2008. Based on TLS 1.1, TLS 1.2 contains improved flexibility. The major differences include:
– The MD5/SHA-1 combination in the pseudorandom function (PRF) was replaced with cipher-suite-specified PRFs.
– The MD5/SHA-1 combination in the digitally-signed element was replaced with a single hash. Signed elements include a field explicitly specifying the hash algorithm used.
– There was substantial cleanup to the client`s and server`s ability to specify which hash and signature algorithms they will accept.
– Addition of support for authenticated encryption with additional data modes.
– TLS Extensions definition and AES Cipher Suites were merged in.
– Tighter checking of EncryptedPreMasterSecret version numbers.
– Many of the requirements were tightened
– Verify_data length depends on the cipher suite
– Description of Bleichenbacher/Dlima attack defenses cleaned up.

RFC 5246: http://tools.ietf.org/html/rfc5246

Resources:
If you would like to read more about SSL or TLS, here are several resources that might be helpful:
TLS – Wikipedia (http://en.wikipedia.org/wiki/Transport_Layer_Security)
SSL versus TLS – What`s the Difference? (http://luxsci.com/blog/ssl-versus-tls-whats-the-difference.html)
Cisco – SSL: Foundation for Web Security (http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_1-1/ssl.html)

As always, if you have any questions or would like to talk to the wolfSSL team about more information, please contact info@wolfssl.com.