信安基础课件翻译chapter4

Chapter 4密钥管理Key Management在整个生命周期管理所有密钥，包括产生、存储、分配、组织、使用、停用、更换、销毁Manage all stages of keys in the whole lifecycle, including the generation, storage, distribution, organization, employment, suspension, update & destruction1、原理Principle▪全程安全All-around Security▪最小权利Minimal Right▪责任分离Responsibility Separation▪密钥分级Key Classification▪密钥更换Key Replacement▪足够长度Enough Length▪针对不同密码体制采取不同管理策略Different cryptosystem, different management policy2、对称密码的密钥管理 Key Management for Symmetric Cipher集权的KDC为每一个会话分配会话密钥，往往是瓶颈和攻击目标Centralization, KDC distributes session key for every session and tends to be the bottleneck and the attacking aim(1)密钥机构Key Organization▪分类Classification–初级密钥Elementary Key:用于数据加解密 used for encrypting & decrypting data •Kc (for 通信communication), Ks (for 会话session), Kf (for 文件file)–二级密钥Secondary Key:用于保护EK used for protecting EK•K NC, K NS, K NF (N----node)–主密钥 Master Key:最高级 the topmost level•K M(2)初级密钥Elementary Key▪Key for encryption & decryption, Kc for communication, Ks for session, Kf for file storage▪由系统的硬件或软件产生，由用户指定Generated by hardware or software of the system, can also be specified by user▪Kc & Ks 是一次一密的，而Kf的生命周期与文件一样长Kc & Ks is one-time pad, while the lifecycle of Kf is as long as the file▪在K的生命周期种，他是受K N保护的K is protected by K N during its lifecycle (3)二级密钥Secondary Key▪保护初级密钥的密钥Key to protect elementary key, K NC for Kc, K NS for Ks, K NF for Kf▪被硬件或软件产生Generated by hardware or software▪生命周期很长Lifecycle is long▪在K N的生命周期中，他是受主密钥保护的 K N is protected by K M during its lifecycle(4)主密钥 Master Key▪在密钥管理系统中最大的密钥The maximal key in key management system▪ 被硬件产生，被安全专家安装/分发Generated by hardware andinstalled/distributed by security experts▪ 有最长的生命周期Have the longest lifecycle(5)密钥生成Key Generation▪ 对不同层的密钥实行不同的策略Different strategies for different level keys ▪ 随机性：长周期，非线性，平等概率，不确定Randomicity: long-period, non-linear,equal-probability, uncertain▪ 高级密钥：真随机High-level key: real-randomicity▪ 低级密钥：伪随机Low-level key: pseudo-randomicity(6)主密钥的生成Generation of Master Key▪ 高质量的真随机序列Real-randomicity sequences with high quality▪ 方式：从电子噪声源或力学噪声源收到的随机模拟信号，转换成自然数码Means:transform the random simulation signals from the nature into digitals, based on the mechanics noise source or the electronics noise source(7)二级密钥生成Generation of Secondary Key▪ 为随机数加密Encrypt the random numbers▪ K N =E(E(E(E(i,RN 1),RN 2),RN 1),RN 3), i is a ordinal number, RN1 & RN2 isreal-random, RN3 is pseudo-random(8)初级密钥生成Generation of Elementary Key▪ 用K N 为伪随机数解密Decrypt pseudo-random numbers by▪ Kc ＝D(RN1,K NC ), Ks ＝D(RN2,K NS ), Kf ＝D(RN3,K NF )▪ 非常快Very fast(9)密钥分配Key Distribution▪ Master Key: 用人力，对大型网络是不实际的by manpower, not practical forlarge network▪ Secondary Key:用主密钥解密，通过网络转换密文 encrypted by master key,then transform the ciphertext via the network▪ Elementary Key:直接转换生成的随机序列，恢复用于解密二级密钥的密钥transform the generated random number directly, recovery the key by decrypting the number using the secondary key二级密钥的分配Key Distribution for Secondary Key初级密钥的分配Key Distribution for Elementary Key(10) Diffie-Hellman 密钥交换Diffie-Hellman Key Exchange ----P213▪ By Diffie & Hellman in 1976 along with the exposition of public key concepts ▪ A practical method for public exchange of a secret key, used in a numberof commercial products▪ Mathematical basis– based on exponentiation in a finite field (modulo a prime) – easy– security relies on the difficulty of computing discrete logarithms 离散对数 (similar to factoring) – hardAnalysis of Diffie-Hellman▪ 不能使所有消息都作为会话密钥交换Cannot be used to exchange an arbitrarymessage as session key but a power▪ 只被两个参与者知道Known only to the two participants▪ 密钥值基于参与者（他们的公有和私有信息）Value of key depends on theparticipants (their private and public information)▪ 攻击需要一个x ，必须解决离散对数问题Attacker needs an x,must solvediscrete log problem(11)中间人攻击Middle-man Attack against Diffie-Hellman P215▪ The attacker Darth generates two random private-information :X D1,X D2,and computes the corresponding public-information :Y D1,Y D2▪ Alice transforms her Y A to Bob▪ Darth intercepts Y A and transform Y D1 to Bob, and calculates K 2=(Y A )XD2 modq▪ Bob receives Y D1, and calculates K 1=(Y D1)XB mod q▪ Bob transforms Y B to Alice▪ Darth intercepts Y B and transform Y D2 to Alice, and calculates K 1=(Y B )XD1mod q▪ Alice receives Y D2, and calculates K 2=(Y D2)XA mod q▪ Result: Bob & Darth share K1, Alice & Darth share K2(12) 密钥存储和备份Key Storage & Backup▪ 原则：在没有密钥管理设备的情况下，密钥是隐藏的Principle: plaintexts of keysare forbidden out of the key management equipments▪ 物理保证：可靠的存储介质Physical assurance: reliable storage medium▪ 管理保证：安全的访问控制机制Managing assurance: secure access-controlmechanism(14)密钥存储Key Storage▪ Master Key:存储在专用的密码设备里，或者直接存储在多个不同地点的密码设备（最小权利） store the plaintext in the appropriative cipher equipments, or store the portions discretely in several equipments even in different places (Minimal Right )▪ Secondary Key: store the ciphertext in the memorizer 存储器▪ Elementary Key: store the ciphertext of Kf in the memorizer, store theciphertext of Kc & Ks in the memory 内存(15)Key Backup▪ 备份也是存储在不同的设备不同的地点Backup is also a storage in differentequipments & different places▪ 备份密钥和初始密钥一样安全The backuped keys are as secure as the originalkeys▪ The low-class keys should be protected by high-class keys in ciphertext ▪ 高级密钥在存储时应被部分地分开The high-class keys in plaintext storageshould be separated in portions▪ 备份应当还原方便The backup should be recovered conveniently▪ 日志记录审计Log recorded for audit(16)密钥更新Key Update▪Master Key: all descendants 后代 ---secondary & elementary keys should be updated▪Secondary Key: all descendants --- correlative elementary keys should be updated▪Elementary Key▪for Kc & Ks, one-time pad, no extra operation▪for Kf, decrypt with former key, encrypt with renewed key (17)Key Suspension停用 & Destruction分配▪密钥在用于加密之后应该被安全的存储和保护直到它们被毁坏Keys should be securely stored & protected after suspension to manage the information encrypted by them until their destruction▪也包括备份的毁坏Destruction includes the backuped keys。