Reading todays new on TechCrunch on how NSA can get rosters from some chat sites (and notably Facebook is missing there!) did some analysis on how its technically possible. So, here is the security analysis for Google Chat site which returns list of buddies (roster) for Google Talk/Hangouts: https://ssllabs/ssltest/analyze.html?d=talk.google Well, at first it has grade A, however, lets look into details: Only 2 cipher suites are offered by the server: TLS_RSA_WITH_RC4_128_MD5 TLS_RSA_WITH_RC4_128_SHA And surprisingly both suites has 2 known vulnerabilities: 1. RC4 is considered as crackable algorithm, e.g. having enough horsepower its theoretically possible to decrypt it having session capture: isg.rhul.ac.uk/tls/ So NSA can just sniff traffic on backbones, filter out one coming from Google talk and then decrypt it. 2. IF NSA somehow (through subpoena and/or warrant) got Googles RSA private key == they can decrypt everything in realtime. Googles crypto suites are not providing protection against that (e.g. RSA key exchange fully depends on attacker not knowing RSA private key. FYI: key exchange is this portion of suite name: TLS_RSA_). 3. MD5 in 2013? Give me a f*ng break! Sha1 is slightly better, however as of 2005 it was demonstrated to have weaknesses, however, those weaknesses are unlikely to be explored by attackers. There are easier ways in. NOTE: as server offers only those 2 crypto suites clients CANNOT pick anything but one of those 2 ways to encrypt your data, both can be easy decrypted. Just for comparison, lets look at what Facebook offers: https://ssllabs/ssltest/analyze.html?d=graph.facebook Well, at first look, same A score, but the list of offered crypto suites is SIGNIFICANTLY bigger: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA 1. Facebook allows for client to opt for AES_256 session encryption. Its stronger than the one required for top secret (AES 192). 2. TLS_ECDHE_ portion in cipher name means that even if somebody got a hold of Facebooks private key they still will be unable to decrypt whats going on. (This key exchange uses additional data to protect session key exchange, while using RSA key just for server authentication purposes). Basically this means, Facebooks clients can opt for non-hackable connection, while Googles cannot. ....
Posted on: Tue, 15 Oct 2013 03:45:24 +0000
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