What are the differences between the versions of TLS?

  • Please correct me if I'm wrong, but my understanding is that SSLv3 and TLSv1 is just a rename of the earlier protocol... but TLSv1 adds the ability to have secured and unsecured traffic on the same port.

    What are the differences and benefits of all the newer specs of TLS?

    I think "TLSv1 adds the ability to have secured and unsecured traffic on the same port" is a misunderstanding due to some application (typically e-mail clients) having a user option they call "SSL" and "TLS" meaning "SSL/TLS from the beginning" or "switching to SSL/TLS via something like STARTTLS" (within the initial application protocol, e.g. SMTP). You can turn a plain socket into an SSL one too (by initiating a handshake as you would with TLS). See http://stackoverflow.com/questions/3660798/what-happens-on-the-wire-when-a-tls-ldap-or-tls-http-connection-is-set-up/3661416#3661416

  • 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:

    "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

    TLS 1.0 [..] 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

    TLS 1.1 [..] 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.

    TLS 1.2 [..] 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.

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Content dated before 7/24/2021 11:53 AM