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Tor 0.3.2.9 釋出,支援下一代的 Hidden Service

Tor 放出了新的 stable 版本:「Tor 0.3.2.9 is released: We have a new stable series!」。

這個版本支援新一代的 hidden service,也就是之前在「下一代的 Tor Hidden Service」這邊提到的東西,將原來 hostname 的部份從 16 chars 變成 56 chars,也就是像 7fa6xlti5joarlmkuhjaifa47ukgcwz6tfndgax45ocyn4rixm632jid.onion 這樣的網址。

這對 hidden service 很重要,因為這代表了淘汰掉舊的演算法,尤其裡面有兩個 (SHA1 與 RSA1024) 都已經確定有問題了:

a) Better crypto (replaced SHA1/DH/RSA1024 with SHA3/ed25519/curve25519)

ROCA:Infineon Technologies 的 RSA 實做問題

最近的另外一個大包,不過這包是 Infineon Technologies 在實做 RSA 算法時的問題,倒不是 RSA 算法本身有問題。之所以會「大」是因為有太多人用了:「ROCA: Vulnerable RSA generation (CVE-2017-15361)」。

起因於 Infineon Technologies 在產生 key 時的組合有限,於是要猜測的 keyspace 小很多。

以研究者的估算,可以看出 CPU year 都被大幅減少了,都是屬於「可行」的範圍:

The time complexity and cost for the selected key lengths (Intel E5-2650 v3@3GHz Q2/2014):

512 bit RSA keys - 2 CPU hours (the cost of $0.06);
1024 bit RSA keys – 97 CPU days (the cost of $40-$80);
2048 bit RSA keys – 140.8 CPU years, (the cost of $20,000 - $40,000).

而且這邊是用 CPU year 估算,如果考慮 FPGA 加速計算,應該會短更多...

另外從發現到公開的時間線也拉得很長,可以看到中間一直在找解決方案:

2nd of November 2017 - Presentation of all details at the ACM CCS conference (to come)
16th of October 2017 - The initial version of the public disclosure published
May to October 2017 - Cooperation with the manufacturer and other affected parties to help evaluate and mitigate the vulnerability
1st of February - The vulnerability disclosed to Infineon Technologies AG
End of January - The vulnerability found

過一陣子就會去 conference 上報告了...

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