crypto4c-ch00-导读
crypto4c-ch08-数论入门
– http://www.cse.iitk.ac.in/users/manindra/
• 比M-R算法要慢
B
找素数实际考虑
• 产生n位的随机数p • 设置p最高位和最低位都为1 以满足是够大的奇数 • 用小素数表试除，确认p不是他们的倍数 3、5、7、11、…、2003等 • 用MR测试法找证据，多找几个，比如5个 * 任何步骤失败，则重新选择p – 或者p递增
B
快速计算 x^y％z
• 优化算法 – 技巧，如中国剩余定理 – 使用预先计算的/中间的结果 • 汇编语言 – MASM、NASM • 硬件芯片 – CPLD、FPGA、ASIC – 资质 • 并行 – 阵列、集群、分布式
B
x^y％z的硬件加速器
• 芯片产品
– 国家监制产品 – 公司商业产品
• SSL加速器
B
• 举例 （p、q都是素数）
Φ(p) ＝ p-1 Φ(p×q) =φ(p)φ(q) ＝(p-1)(q-1) ＝pq-p-q+1
• 比如n=15 n＝15＝3×5＝p×q
则φ(n)＝(3-1)×(5-1)＝8 即 8：1、2、4、7、8、11、13、14
B
欧拉定理
• 如果a、n互素，则 aφ(n)≡1 mod n aφ(n)＋1≡ a mod n 或即
• 比如n＝15＝3×5 ，φ(n)＝8 1、2、4、7、8、11、13、14 ≡1 mod 15 而 3、 5、 6、9、10、12 ≠ 1 mod 15 • 证明见备注
B
crypto加密原理
crypto加密原理Crypto, short for cryptography, is the practice and study of techniques for secure communication in the presence of third parties. It is used to secure the information and communication between parties through the use of codes and ciphers.加密，即密码学，是在第三方存在时用于安全通信的技术的实践和研究。
它用于通过使用代码和密码来保护各方之间的信息和通信。
One of the key principles of cryptography is the use of algorithms to encrypt and decrypt messages. These algorithms use keys to perform the encryption and decryption processes, ensuring that only the intended recipients can access the information.密码学的一个关键原则是使用算法来加密和解密消息。
这些算法使用密钥来执行加密和解密过程，确保只有预期的接收者才能访问信息。
There are two main types of cryptography: symmetric and asymmetric. Symmetric cryptography uses the same key for both encryption and decryption, while asymmetric cryptography uses apair of public and private keys for the encryption and decryption processes.密码学主要有两种类型：对称加密和非对称加密。
linux kernel crypto的用法
Linux内核提供了丰富的加密和密码学功能，这些功能可以在内核中使用，而不需要依赖用户空间的库或工具。
这些功能包括对称加密、非对称加密、哈希函数、伪随机数生成和数字签名等。
以下是一些常见的Linux 内核crypto 库的用法示例：1. **对称加密**：使用内核的对称加密API，你可以进行对称加密操作，如AES、DES等。
下面是一个使用AES 加密的示例：```c#include <linux/crypto.h>#include <linux/scatterlist.h>#include <crypto/skcipher.h>/* 加密函数*/void aes_encrypt(const u8 *input, u8 *output, struct crypto_skcipher *tfm){struct skcipher_request *req = NULL;struct scatterlist sg_in, sg_out;int ret;req = skcipher_request_alloc(tfm, GFP_KERNEL);if (!req) {printk(KERN_ERR "skcipher_request_alloc failed\n");return;}sg_init_one(&sg_in, input, AES_BLOCK_SIZE);sg_init_one(&sg_out, output, AES_BLOCK_SIZE);skcipher_request_set_crypt(req, &sg_in, &sg_out, AES_BLOCK_SIZE, NULL);ret = crypto_skcipher_encrypt(req);if (ret) {printk(KERN_ERR "crypto_skcipher_encrypt failed: %d\n", ret);}skcipher_request_free(req);}```2. **非对称加密**：你也可以在内核中使用非对称加密，如RSA。
crypto4c-ch01-引言
B
被动攻击
（1）对传输中的明文进行窃听,导致信息泄露
– 许多软件可做到 (如嗅探器等)
（2）流量分析(针对密文)
– 可以得到统计和模式信息
• 身份,位置,频度,长度等
• 难于检测 重在预防
B
主动攻击
（1）重放 （2）伪装/假冒 （3）篡改 （4）拒绝服务（阻断） • 难于预防 重在检测
B
1.4 安全服务
B
网络安全模型
• 要素（1）安全变换（加密等） （2）共享秘密（密钥等）
B
网络访问安全模型
• 两种体现形式 对应的机制 （1）黑客 （1）门卫 （2）病毒等恶意代码 （2）监控程序
B
ISO 7498-2: 安全框架
• ISO 7498-2
– 阐述ISO/OSI中分层和安全服务的对应 – 服务和机制 – 服务、机制与层的关系 – 各层中安全服务与安全机制的配置 – 安全管理
• 查阅 ISO 7498-2
B
7498 (层次, 机制, 服务)
•
B
1.3 安全攻击
分两类 • 被动攻击 • 主动攻击
B
安全弱点和报告事件统计
• by CERT
B
安全趋势
•
B
1.2 OSI安全框架
• X.800
– 为OSI(开放式系统互联)定义安全框架 – 推荐 X.800 与 ISO 7498-2
• ISO 7498-2
– 信息处理系统 – 开放式系统互联 – 提供基本参考模型
B
OSI安全框架
• RFC2828给出了威胁和攻击的概括 （1）威胁：是弱点，是可能性 （2）攻击：是源于威胁的行为 {表1.1} • X.800 安全攻击 安全机制 安全服务
Introduction to Cryptocurrencies
Introduction to Cryptocurrencies∗Stefan Dziembowski†University of WarsawS.Dziembowski@.plABSTRACTWe provide a research-oriented introduction to the crypto-graphic currencies.We start with a description of Bitcoin and its main design principles.We then discuss some of its weaknesses,and show some ideas for dealing with them.We also talk about the mechanics of the mining pools and ideas for discouraging the mining pool creation.We provide an introduction to the smart contracts,and give some examples of them,including the multiparty lotteries.We then present alternative currencies that were designed to remedy some of the problems of Bitcoin.In particular, we talk about the Litecoin,the Primecoin,the Permacoin, the Zerocoin,the Proofs of Stake and the Proofs of Space. We also discuss the most important research challenges in this area.Categories and Subject DescriptorsK.4.4[Computing Milieux]:Computers and Society–Payment schemes;Distributed commercial transactions;Cy-bercash,digital cashKeywordscryptocurrencies;distributed cryptography1.INTRODUCTIONThe cryptographic currencies(also dubbed the cryptocur-rencies)are a fascinating recent concept whose popularity exploded in the past few years.Their main distinguishing feature is that they are not controlled by any single entity.∗A longer version of this document is available at .pl/Dziembowski/talks/bitcoin-tutorial.pdf.Slides from this tutorial are available at.pl/Dziembowski/talks.†Supported by the Foundation for Polish Science WELCOME/2010-4/2grant founded within the frame-work of the EU Innovative Economy(National Cohesion Strategy)Operational ProgrammePermission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full cita-tion on thefirst page.Copyrights for third-party components of this work must be honored.For all other uses,contact the Owner/Author(s).Copyright is held by the owner/author(s).CCS’15,October12–16,2015,Denver,Colorado,USA.ACM978-1-4503-3832-5/15/10.Instead,they are jointly maintained by their anonymous users connected via peer-to-peer networks.Their security is based purely on the security of the underlying crypto-graphic primitives,and on some global assumptions about the behavior of their users(like,e.g.,an assumption that a large fraction of the computing power is controlled by the honest participants).Historically thefirst,and the most prominent cryptocur-rency is the Bitcoin,introduced in2008by Satoshi Naka-moto[9].Probably the most intriguing technical innovations of Bitcoin are:the mechanism for reaching consensus in fully distributed peer-to-peer networks(the so-called blockchain technology),and the transaction syntax that allows to ex-ecute distributedfinancial operations that are much more complex than simple money transfers.Even the sheerfinancial importance of the cryptocurencies makes them an interesting research area.In our opinion, however,what makes this topic even more fascinating are the conceptual ideas behind it.These aspects will be the main focus of this tutorial.Goal of this tutorial.The goal of this tutorial is to provide a research-oriented introduction to the cryptocur-rencies.We will present the main principles of the Bitcoin design,discuss some of its weaknesses,show some ideas for its improvements and for other currencies,and discuss the most important research challenges in this area.Intended audience and prerequisite knowledge. This tutorial will be suitable for all the ACM CCS partic-ipants,both coming from the academia and from the in-dustry.We will assume familiarity with the basic crypto-graphic primitives,such as the hash functions,the signature schemes,and encryption.No prior knowledge of Bitcoin or other cryptographic currencies is required.2.OVERVIEW2.1IntroductionWe will start with a brief overview of the history of the cryptocurrencies.We will identify the mainfinancial and social aspects that contributed to the success of Bitcoin,and mention some opinions of prominent economists about the cryptocurrencies,both those supporting this idea,and those that are skeptical about it.We will show how the popularity of Bitcoin grew over time,and how its pricefluctuated.We will also mention some important events in the history of the Bitcoin community(like the MtGox collapase).DOI: /10.1145/2810103.2812704.We will introduce the transaction ledger(the blockchain), as a technique that can be used to prevent double-spending of electronic cash.We will point out that the Sybil attacks should be taken into account when designing a protocol that emulates such a ledger.We will explain what are the Proofs of Work(PoWs)and how to apply them to thwart the Sybil attacks.We will show how the Bitcoin ledger is maintained by the users called miners that solve the PoWs,in a process called mining.We will explain the concept of the hashrate and show how the total hashrate of Bitcoin users changed over the time.We will also describe how the hardness of Bitcoin’s PoW’s is adjusted to the changing hashrate.We will also talk about the Bitcoin transaction syntax.2.3Bitcoin mining poolsMining pools are coalitions of miners that share the re-ward from mining new blocks.We will discuss the economic reasons for joining the mining pools(reducing the variance of the mining reward).We will then talk about the mechan-ics of the mining pool reward systems and their weaknesses. We will also show how mining pools can be decentralized vie the so-called peer-to-peer mining technique.Discouraging the mining pool creation.We will ex-plain the risks behind the pooled miming.In particular,we will point out that it leads to the centralization of the control over mining.We will then discuss some ideas for the Bitcoin modifications that discourage the mining pool creation[8].2.4Security weaknesses of BitcoinWe will discuss the quality of the Bitcoin design.We will mention some incidents when programming errors lead to forks that needed to be resolved“manually”and we will explain the transaction malleability problem.We will then present more fundamental problems with the blockchain technology.In particular we will explain the self-ish mining attack introduced in the groundbreaking paper of Eyal and Sirer[6]and the difficulty raising attack of Lear Bahack[3]that exploits the way in which the miming dif-ficulty is adjusted in Bitcoin.We will also talk about the birbery attacks of[5].2.5Smart contractsOne of the most intriguing properties of Bitcoin is the pos-sibility of creating the so-called smart contracts(originally proposed in1990s by Nick Szabo).Such contracts can be viewed asfinancial agreements between a number of parties, whose implementations are enforced by the Bitcoin system. Simple examples of such agreements include the escrow and dispute mediation,and the assurance contracts.More ad-vanced types of contracts are the fair multiparty protocols, and in particular the decentralized lotteries[2,1,4].We will give an overview of this area.2.6Other cryptocurrenciesDiscouraging hardware mining.One of the problems of Bitcoin is that mining in hardware is much more efficient than mining in software,and hence it is completely infeasi-ble nowadays to be a miner without investing in specialized hardware.We will describe the Litecoin,which is a cur-rency that was supposed to have the property that it is not economical to mine in hardware.Less“wasteful”cryptocurrencies.Another problem with the Proofs of Work is that they require the miners to spend significant amounts of electricity on mining.There are essentially two approaches to create less“wasteful”cryp-tocurrencies.Thefirst one is to create a cryptocurrency where the work is spent on some“useful”task.We will give an overview of the currencies belonging to this class:the Permacoin,and the Primecoin.The second approach is to replace“work”by some other type of resource.This includes the Proofs of Stake,and the Proofs of Space,which is used in the recent Spacecoin proposal.We will give a short overview of these approaches.More anonymity.Since the Bitcoin’s transaction ledger is public,the only anonymity in this system comes from the fact that the users are using pseudonyms,instead if their real names.As recently shown in[7]this does not provide sufficient privacy protection.We will briefly talk about this result,and then we will explain(on a high level)the main design principles of Zerocash,which is a new proposal for a currency that provides true anonymity.2.7Research directionsWe will conclude with an overview of the open research problems in this area,like the need for better understand-ing of the Bitcoin security model,and improvement of the blockchain technology.We will also mention the open prob-lems concerning the distributed contracts,in particular we will discuss what obstacles need to be overcome to make them really practical.Finally,we will also describe the problems with securely storing the Bitcoin secret keys(in the so-called wallets).3.REFERENCES[1]M.Andrychowicz,S.Dziembowski,D.Malinowski,and L.Mazurek.Fair two-party computations viaBitcoin deposits.In BITCOIN workshop in association with the Financial Cryptography and Data Securityconference,2014.[2]M.Andrychowicz,S.Dziembowski,D.Malinowski,and L.Mazurek.Secure multiparty computations onBitcoin.In2014IEEE Symposium on Security andPrivacy[3]L.Bahack.Theoretical bitcoin attacks with less thanhalf of the computational power.arXiv,2013.[4]I.Bentov and R.Kumaresan.How to use bitcoin todesign fair protocols.In CRYPTO2014[5]J.Bonneau,E.W.Felten,S.Goldfeder,J.A.Kroll,and A.Narayanan.Why buy when you can rent?Bribery attacks on Bitcoin consensus,November2014.manuscript[6]I.Eyal and E.G¨u n Sirer.Majority is not enough:Bitcoin mining is vulnerable.In FinancialCryptography and Data Security,2014.[7]S.Meiklejohn,M.Pomarole,G.Jordan,K.Levchenko,D.McCoy,G.M.Voelker,and S.Savage.Afistful ofbitcoins:Characterizing payments among men withno names.In Proceedings of the2013Conference onInternet Measurement Conference.[8]ler,E.Shi,A.Kosba,and J.Katz.Preprint:Nonoutsourceable scratch-offpuzzles to discouragebitcoin mining coalitions.2015.[9]Satoshi Nakamoto.Bitcoin:A peer-to-peer electroniccash system,2008.2.2Bitcoin main design principles。
crypto4c-ch02-古典密码技术
B
Playfair实现
• 缩小对照表的规模(简化)
– 676项 →5×5字母矩阵
明文双字母α β →其对称对角线上的双字母
• 如 hs → BP, tm → LR • 规定
– I同J（或U同V） – 同行者取右，同列者取下
– ar → RM，mu→ CM
M O N A R C H Y B D E F G J K L P Q S T U V W X Z
abcdefghijklmnopqrstuvwxyz DKVQFIBJWPESCXHTMYAUOLRGZN if we wish to replace letters WI RF RWAJ UH YFTSDVF SFUUFYA WI RF RWAJ UH YFTSDVF SFUUFYA if we wish to replace letters ABCDEFGHIJKLMNOPQRSTUVWXYZ sgmakexofhbv Confusion 混乱
Transposition 置换 Substitution 代换
– 把明文重新排列分散
– 以掩盖明文和密文的关系
B
密码学的新方向
• New Directions in Cryptography
– Whitfield Diffie and Martin E. Hellman, 1976
• （已经知道算法） • 先得有足够多的密文
– 几十个 – 明文得有明确的意义(古典算法时通常是这样的)
• 统计密文中各个字母的出现概率 • 结合明文的统计
– 猜测出现得最多密文字母对应明文字母e(或t、a) ，最少的是z(或j) – 猜测出现得最多密文双字母组合是th – 观察所谓的明文，并重试
B
crypto++例子
crypto++例子Crypto++（也被称为CryptoPP）是一个C++库，提供了大量的加密和解密算法。
以下是一个使用Crypto++库进行AES加密和解密的简单示例：首先，你需要安装Crypto++库。
你可以从其官方网站下载源代码并编译安装，或者使用包管理器如apt或brew进行安装。
下面是一个使用Crypto++库进行AES加密和解密的C++代码示例：cpp复制代码：#include <iostream>#include <string>#include <cryptopp/aes.h>#include <cryptopp/modes.h>#include <cryptopp/filters.h>#include <cryptopp/hex.h>int main() {// 密钥和初始化向量std::string key = "0123456789abcdef"; // 16字节密钥std::string iv = "abcdef0123456789"; // 16字节初始化向量// 待加密的数据std::string plaintext = "Hello, world!";try {// 创建AES对象，设置密钥和初始化向量CryptoPP::AES::Encryption aesEncryption(key.c_str(), CryptoPP::AES::DEFAULT_KEYLENGTH);CryptoPP::CBC_Mode_ExternalCipher::Encryption cbcEncryption(aesEncryption, iv.c_str());// 加密数据std::string ciphertext;CryptoPP::StreamTransformationFilterstfEncryptor(cbcEncryption, new CryptoPP::StringSink(ciphertext));stfEncryptor.Put(reinterpret_cast<const unsigned char*>(plaintext.c_str()), plaintext.length() + 1);stfEncryptor.MessageEnd();// 输出加密后的数据（以十六进制形式）std::cout << "加密后的数据（十六进制形式）: " << CryptoPP::Hex::Encode(ciphertext) << std::endl;// 解密数据std::string decryptedtext;CryptoPP::StreamTransformationFilterstfDecryptor(cbcDecryption, new CryptoPP::StringSink(decryptedtext));stfDecryptor.Put(reinterpret_cast<const unsigned char*>(ciphertext.c_str()), ciphertext.length());stfDecryptor.MessageEnd();// 输出解密后的数据std::cout << "解密后的数据: " << decryptedtext << std::endl;} catch (const CryptoPP::Exception& e) {std::cerr << "加密或解密过程中发生错误: " << e.what() << std::endl;}return 0;}这个例子使用了AES算法，CBC模式，和16字节的密钥和初始化向量。
dm-crypt crypto原理
dm-crypt crypto原理
DM-Crypt是一种在Linux内核中实现磁盘加密的技术，它使用cryptographic algorithms（加密算法）来保护存储设备上的数据。
以下是DM-Crypt加密原理的简要概述：
1. 初始化阶段：当一个加密设备被挂载时，它首先需要被初始化。
这个过程包括生成一个密钥（通常是AES或其他对称加密算法），并使用它来加密存储设备上的数据。
2. 加密和解密：在加密和解密数据时，DM-Crypt使用对称加密算法（如AES）进行加密和解密操作。
加密过程使用生成的密钥对数据进行加密，使得只有拥有正确解密密钥的用户才能访问数据。
解密过程则使用相同的密钥对数据进行解密，以恢复原始数据。
3. 存储设备访问：当操作系统需要访问加密设备上的数据时，它首先需要与cryptoloop或cryptfs等驱动程序进行交互。
驱动程序会检查请求的数据是否已经被加密，并根据需要使用密钥进行解密或加密操作。
4. 密钥管理：DM-Crypt使用一个主密钥（Master Key）来管理和保护其他密钥。
主密钥通常存储在另一个加密设备上，只有拥有正确访问权限的用户才能访问它。
主密钥用于生成用于加密和解密其他设备的密钥。
总的来说，DM-Crypt通过使用对称加密算法对存储设备上的数据进行加密，并使用主密钥进行管理和保护，确保只有拥有正确访问权限的用户才能访问加密设备上的数据。
这种技术通常被用于保护重要数据的安全性和保密性。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
B
参考书目
• Handbook of Applied Cryptography
– Alfred J. Menezes
• http://www.cacr.math.uwaterloo.ca/hac/
– 英文电子版
• 应用密码学手册
– 中译本 胡磊 – 电子工业出版社
B
密码编码学与网络安全
—— 原理与实践(第四版)
中译本 孟庆树等译
电子工业出版社
B
第0章 导读
• 本课程内容分为4个部分
– 对称密码 – 公钥密码 – 网络安全 – 系统安全
前两个是密码学基础，后面是应用。
密码学和信息安全 能帮助我们干什么
• 通信安全
– 偷听和保密
• 分组网络的存储-转发
B
– 假冒和抵赖
• 第4版
– 中译本 孟庆树 等 – 电子工业出版社
B
参考书目
• Applied Cryptography: protocol, algorithms, and source code in C，(2ED)
– Bruce Schneier• http://wwwFra /• 应用密码学 第2版
– 网络体系结构(ISO/OSI)和网络协议(TCP/IP) – 操作系统和系统软件
• 密码学原理
– 密码算法，密码协议
• 安全标准和安全体系
– 安全算法和协议的标准，安全框架
• 安全应用专题
– – – – 系统安全，包括操作系统、服务器软件 PKI专题 邮件、 文件、 磁盘等加密 Virus, Firewall, VPN, SSL, Kerberos等
B
参考书目
• Cryptography and Network Security : Principles and Practice, 4ED
– by William Stallings
• /Crypto4e.html
• 密码编码学与网络安全：原理与实践
• 无纸化支持
– 办公和电子商务活动 – 签章、支付安全和抵赖问题 – 数字签名
• 系统安全
– 漏洞、病毒等问题
B
课程目标
• • • • 了解网络信息安全的主要问题、分类 学习解决安全问题的理论、技术、方案 使用、构建和部署安全产品和系统 引导网络安全方面的开发和研究兴趣
B
主要内容
• 网络和系统的安全问题