Come from:Bip32(https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki): derivation.png

對於大多數有在使用區塊鏈交易的人,他們都會知道有一個神聖不可遺失的東西稱作:助記詞。其中的技術是利用 BIP32 所描述的一個固定性推導方式而產生私鑰。這個概念的引入是為了配合比特幣原先的初衷:任何交易賬戶只使用一次。若是要滿足這個需求,大家需要管理非常多的私鑰,故導致管理私鑰的難題。此外,隨著各種鏈的興起,這項技術也被拿來應用在生成各種不同鏈的私鑰。

簡單來說,BIP32 主要規範了三種類型的推導方式:


Like other permission-less blockchains and cryptocurrencies, Ethereum obtains consensus using a form of cryptographic zero-knowledge proof called “Proof-of- work“. In such protocols, a character called “miner”, groups transactions into a block and appends it to the end of blockchains. This work is resource consumptive, and thus, operations using Ethereum require a fee, which is received by miner in exchange for performing the work. Each block on the chain has an upper bound on the amount of gas that can be included in it, so miners maximize profit by prioritizing transactions offering higher gas prices. It produces a challenging question: how…


AMIS 是 Wallet Service 提供者。除了應用各種基本的安全加密技術,也積極地發展一些先進的密碼技術以強化系統安全。近期 AMIS 除了發佈跨雲備份之技術,更基於安全管理和私鑰之使用而開發 Alice 套件。開放 Alice 不僅是對本公司自行開發之套件深具信心,更是讓其他先進了解並進而檢核我們技術開發的嚴謹性。期許此套件能對整個區塊鏈社群發展產生正向的助益。HTSS 尚有其他發展的可能,歡迎任何有興趣的團隊與我們合作。

目的:

AMIS 開源 Library(Alice):Hierarchical Threshold Signature Scheme。這是一個更安全使用數位簽章的套件,包含:


The library, Hierarchical Threshold Signature Scheme(abrev. HTSS) worked by AMIS, offers three protocols:


In honour of opening sourced HTSS-Lib https://github.com/getamis/alice worked by AMIS, we revise this topic: Hierarchical Threshold Signature.

Digital Signature:

Digital signature is a digital analogue of a pen-and-ink signature on a physical document. The purpose of digital signature is to solve the following scenario. Alice has a digital document and wants to attach some “proof” that can be used to prove that she had approved this document. Therefore, digital signature can be recognized as an analogue to her handwritten signature on an ordinary document.

Therefore, it is very critical to clarify and confirm that who had signed the contract. In order to…


前言

在目前的實務上,最常使用的同態加密是 Paillier cryptosystem。是一種非對稱式加密:會有一組公鑰用來加密,一組私鑰用來解密。並且在這情況使用的是 RSA 模組。更具體的說就是公鑰有兩個參數決定:

1. N 決定了安全性滿足

這裡的p ,q 是兩個相異質數。

2. 另一個參數是可隨意選取的亂數 g in [2, N²] 並且 g 和 N 互質。

如同 RSA 的狀況,在 Paillier 的系統中,如果 N 被人家分解出是哪兩個質數,那這個加密法基本上就宣告被破解。因此對於實務上的應用至少 N 的長度至少要 2048-bits 以上。

基本功能

基本上大多數的同態加密都一定有以下這三個 functions : KeyGeneration, Encryption, Decryption。在 Pai …


前言:

在這篇短文,我們簡介同態加密( homomorphic encryption) 的基本概念,以及應該具有的密碼學性質。

之後會在系列文章給予兩個例子 (asymmetric algorithm):Paillier 和 C.L. homomorphic encryption。並且在例子 Paillier 解釋為何滿足同態加密的特性。在 C.L. homomorphic encryption 我們點出在應用上為何它比 Paillier 更優越之處。

什麼是同態加密( homomorphic encryption):

同態加密指的是一種加密方式,使得使用者可以對密文做計算,計算出來的結果,再做解密的時候的明文是預期的計算結果。

舉個例,當用戶想要做大量的統計數據,但是他的個人電腦無法執行這些大量的計算。由於資料可能是敏感的,因此不能直接明文的跑在雲端超強電腦計算。 …


Introduction:

Key management plays a significant role in blockchain technology regarding digital assets protection. Practically speaking, losing private keys leads to great losses. Improper key management and poor system implementation may increase the risk of asset being transferred maliciously. Take an extreme case that happened before as an example, a principal died suddenly and no one was able to recover keys so that the whole asset was frozen. To solve these problems, experts therefore propose threshold cryptography to reduce the risk of key management.

Threshold Cryptography

In an untrusted system, all participants may not know each other, so we should come up with…

ChihYun Chuang

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