I like this blog entry by yaSSL describing the differences: http://www.yassl.com/yaSSL/Blog/Entries/2010/10/7_Differences_between_SSL_and_TLS_Protocol_Versions.html
I copied the key snippets from the blog to here:
[..] 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
[..] 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
[..] 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.
[..] 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
- 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
- Many of the requirements were tightened
- Verify_data length depends on the cipher suite
- Description of Bleichenbacher/Dlima attack defenses cleaned up.