Security Now 185
|Hosts: Leo Laporte and Steve Gibson|
Topic: Hash Message Authentication Codes
Security Now: 185
News & Errata
09:00 - 16:43
- Autorun wasn't working right before an update from Microsoft KB950582 Steve will be talking about this in detail in the future (Episode 187). There is an option even with the update installed though to force it to function in the previous manner.
16:44 - 19:04
- FreeBSD v7.x Telnet Daemon has a remote code execution exploit which was recently discovered, an existing file on the system could be executed by manipulating environment variables.
19:05 - 22:34
- The recent critical patch for IE7 was reverse engineered and an exploit is now in the wild. It is currently being distributed as a word document via email with an embed ActiveX object. That opens IE and takes you to a site that uses a script to install malware.
22:25 - 30:07
- Two concerning bills in the congress in the US, "Internet Stopping Adults Facilitating the Exploitation of Today's Youth Act". This means anyone assigning IP's via DHCP has to log all activity on the network and keep the logs for at least two years.
30:08 - 33:25
- Zero Day exploit in Adobe Acrobat reader in the wild with no patch currently available until March 11th for version 9 and 18th for version 7 and 8. A temporary fix is to disable scripting.
33:26 - 43:10
- Steve's Kindle 2 has arrived
44:11 - 44:28
- Steve will be on appearing on Maxwells House on Twit Live at 2pm PST 5pm EST on Thursday 26th February 2009. The audio will be put out on the Security Now feed and called 185A.
51:50 - 53:39
- You can bypass security token requirement on PayPal if you leave Ebay to pay for an item on Paypal and give them your email address and password. Once you are asked for the token go back one page and you are logged into your account without having to enter the security token code.
53:40 - 55:30
- Leos Kindle arrived
44:29 - 48:14
A listeners daughters computer wouldn't boot and she didn't have backups of her critical data. He ran Spinrite on the drive and it took an hour fnding 2 unrecoverable sectors. The computer booted fine afterwards and she could copy all of her data off onto an external drive.
Hashed Message Authentication Codes (HMAC)
51:13 - 51:50, 55:30 - 01:15:14
- You encrypt a message to hide its contents.
- Sometimes you want to ensure no changes occur to it in transit you can do this by putting the document through a cryptographic digest and you get out a token which is based on the input.
To sign a message you:
- Hash a document through a digest function.
- Encrypt the token you get out with your private key.
To verify the signature the recipient:
- Hashes the message they receive
- Decrypt your token
- Verify it's the same.
- If a hacker has control over the creation of the documents they can control the output of the hash function.
- If you use HMAC instead then a weaker hash can be made more secure due to using a key
Benefits of Hash's:
- Don't have export restrictions
- Are more open
- Less computationally intensive
- Incorporate a key into the hash function
- With a hash if you put the same thing in you always get the same thing out
- Initially the key was just put at the front of the message before hashing, this was insecure though due to an attack against hash being altering there length but not contents.
- Next the key and the length of the message was put in the hash
- Then they put the key at the beginning and the end of the message
To hash a message using HMAC
- Take the key and XOR it with 512 bits of Hex 36
- Put this in the has followed by the rest of the message
- Take the output of the has and the same key.
- XOR the Key with 512 Bits of Hex 5 C
- Hash the result of this with the output of the first hash
- It is secure because to break it they need to know the output of the first hash
- It is used in SSL
- Astaro Internet Security
- Ad Time0:33-0:44: and 03:24-07:00
- Recorded Date: February 25, 2009
- Release Date: February 26, 2009
- Duration: 1:20:15
- Log line:
- Edited by: Tony
- Notes: Removed Steve coughing at 1:04:37
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