Tag Archives: data

Quotient filter

之前有提過「Cuckoo Filter:比 Bloom Filter 多了 Delete」,最近在「A general purpose counting filter: making every bit count」這邊看到 Quotient filter,也是類似 Bloom filter 的資料結構,但想要解決更多問題。 一般的 Bloom filter (BF) 會有這些問題: The inability to delete items Poor scaling out of RAM The inability to resize dynamically The … Continue reading

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在飯店裡攻擊企業的高階主管

算是為什麼企業要提供 Full Routing VPN 的一個攻擊管道的說明... 這篇介紹了在飯店裡透過 WiFi 攻擊企業的高階主管,想辦法塞木馬取得資訊,或是滲透進企業內部的網路:「Hackers are using hotel Wi-Fi to spy on guests, steal data」。 Those behind the campaign have continually evolved their tactics and malware payloads, blending phishing and social engineering with a complex Trojan, in … Continue reading

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對 Open Data 的攻擊手段

前陣子看到的「Membership Inference Attacks against Machine Learning Models」,裡面試著做到的攻擊手法: [G]iven a data record and black-box access to a model, determine if the record was in the model's training dataset. 也就是拿到一組 Open Data 的存取權限,然後發展一套方法判斷某筆資料是否在裡面。而驗證攻擊的手法當然就是直接攻擊看效果: We empirically evaluate our inference techniques on classification models … Continue reading

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最近 OpenVPN 的安全性漏洞...

看到「The OpenVPN post-audit bug bonanza」這個只有苦笑啊... 作者在 OpenVPN 經過一連串的安全加強後 (包括 harden 計畫與兩個外部單位的程式碼稽核找到不少問題),決定出手挖看看: After a hardening of the OpenVPN code (as commissioned by the Dutch intelligence service AIVD) and two recent audits 1 2, I thought it was now time for some … Continue reading

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Reddit 在處理 Page View 的方式

Reddit 說明了他們如何處理 pageview:「View Counting at Reddit」。 以 Reddit 的規模有提到兩個重點,第一個在善用 Redis 的 HyperLogLog 這個資料結構,當量大的時候其實可以允許有微小的誤差: The amount of memory varies per implementation, but in the case of this implementation, we could count over 1 million IDs using just 12 kilobytes of space, … Continue reading

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ScyllaDB 1.7 支援 Counters 了

在「Scylla release: version 1.7」這邊看到 ScyllaDB 支援 Counters 的消息了 (雖然剛出來,掛著 Experimental 的消息): Scylla now supports Counters as a native type. A counter column is a column whose value is a 64-bit signed integer and on which two operations are supported: incrementing … Continue reading

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在面試時的資料結構與演算法的問題

在「500 Data structures and algorithms interview questions and their solutions」這邊看到在 Quora 上整理出來的題目 (以及解答)。 每個題目下面也都有地方可以留言,等久一點應該會更豐富? 另外一個不錯的地方在於題目的分類,舉例來說,如果想要練習 Backtracking,可以去翻對應的題目出來練。

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AWS EU (Stockholm) Region

由老大 Werner Vogels 出來講一些細節... AWS EU (Stockholm) Region 預定在 2018 年開張營業:「Välkommen till Stockholm – An AWS Region is coming to the Nordics」。 The new AWS EU (Stockholm) Region will have three Availability Zones and will be ready for customers to … Continue reading

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在 ext4 上的 CCFS

在「Application crash consistency and performance with CCFS」這篇看到的東西。 CCFS 目標是拉高 ext4 的 data integrity,並且還是有高效能: CCFS (the Crash-Consistent File System) is an extension to ext4 that restores ordering and weak atomicity guarantees for applications, while at the same time delivering much improved … Continue reading

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Google 的 Guetzli,對 JPEG 的壓縮演算法

Google Research Europe 推出的演算法,在不動 decoder 的情況下,要怎麼樣壓出又小又清晰的 JPEG 圖片:「Announcing Guetzli: A New Open Source JPEG Encoder」,論文可以在「Guetzli: Perceptually Guided JPEG Encoder」這邊下載,程式碼則可以在 GitHub 上的 google/guetzli 取得。 othree 也寫了一篇「Guetzli: A New Open Source JPEG Encoder」介紹 Guetzli。 Guetzli 在同樣的品質下,比現有的壓縮法可以再壓榨出 29%~45% 的空間,這算是非常驚人的數字: We reach a 29-45% … Continue reading

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