Open rainit2006 opened 4 years ago
ブロック暗号(Block cipher). Pretty Good Privacy (PGP) v2.0 で使われていた。 IDEAのブロック長は64ビットで、128ビットの鍵を使う。ラウンドと呼ばれる同じ操作を8回行い、最後に出力段の変換(ハーフラウンド)を行う。 なお、Transport Layer Security (TLS) においてもIDEAを利用可能であったが、実運用でほぼ使われていないことを理由として、TLS 1.2で削除されている.
換字式暗号. 平文を、1文字または数文字単位で別の文字や記号等に変換することで暗号文を作成する暗号である。 A Caesar cipher, rotation cipher or shift cipher is a simple substitution cipher where the cleartext is shifted a number of times up or down a known alphabet.
The Caesar cipher is a shift cipher that works on a stream of text and is also a substitution cipher. シーザー暗号は単一換字式暗号の一種で、平文の各文字を、辞書順に3文字分シフトして暗号文を作る暗号である. 古代ローマの軍事的指導者ガイウス・ユリウス・カエサル(英語読みでシーザー)が使用したことから、この名称がついた。
SSL(Secure Sockets Layer)を利用してデータの暗号化を行うHTTPS方式がある。 SHTTPは送信データを暗号化してセキュリティを高めるのに対して、HTTPSは通信経路自体をセキュアにするという違いがある。
a function that is easy to compute in one direction, yet difficult to compute in the opposite direction (finding its inverse) without special information, called the "trapdoor". Trapdoor functions are widely used in cryptography.
暗号理論における情報伝達手法の一つで、相手に秘密情報そのものを知らせないまま、自分が秘密情報を知っていることを相手に知らせる方法のことである。
1980年代と1990年代に米国政府によって発行された一連のコンピューターセキュリティ標準とガイドラインです。これらは当初、米国国防総省のコンピュータセキュリティセンターによって発行され、その後、国立コンピュータセキュリティセンターによって発行されました。
AES was developed to improve upon DES’s security and flexibility. It uses 128-, 192-,and 256-bit keys (注意没有64bit) アメリカ国立標準技術研究所(NIST)の主導により公募され、Rijndael(ラインダール)がAESとして採用された。 Rijndael, a block symmetric cipher created by Vincent Rijmen and Joan Daemen, was selected as the new AES algorithm.
https://www.youtube.com/watch?v=lnKPoWZnNNM 暗号化処理は始めに鍵生成を行う。AES暗号の鍵長によって変換のラウンド数が異なる。次の通りである。
なお、復号は上記処理の逆変換を逆順で実行する。
DES is a symmetric encryption algorithm that uses a 64-bit key for encryption, but 8 bits of the key are used for parity. Thus, the true key is 56 bits. Itis also a block cipher, not a stream cipher.
IBM's 128-bit algorithm, Lucifer, was accepted as the national standard in 1974. It was altered by NIST and referred to as Digital Encryption Algorithm, which used a 56-bit key. Luciferは、ホルスト・ファイステルらがIBMにて開発したいくつかの初期の民間用ブロック暗号の総称である。DESの基になった。Luciferのうちの1つは DTD-1 という名称で1970年代に銀行で使われていた。
、共通鍵ブロック暗号であるDESを3回施す暗号アルゴリズム。正式名称はTriple Data Encryption Algorithm(TDEA、Triple DEA)。アメリカ国立標準技術研究所は2030年までに使用をやめるよう推奨している。 DES-EEE3 uses three keys for encryption and the data is encrypted, encrypted, encrypted; DES-EDE3 uses three keys and encrypts, decrypts and encrypts data. DES-EEE2 and DES-EDE2 are the same as the previous modes, but the first and third operations use the same key. There is no DES-EEE1.
Pretty Good Privacy (PGP) is a security program focused on protecting e-mail messages. It uses public key encryption by implementing a “web of trust" among users. In contrast to certificate authorities, which control the levels of trust, PGP allows users to sign each others' public keys, thus developing a trusted network. PGP也用于session key加密
The Digital Signature Standard approves three encryption algorithms for use in digital signatures
Under the Common Criteria model, an evaluation is carried out on a product and it is assigned an Evaluation Assurance Level (EAL) • EAL1 Functionally tested • EAL2 Structurally tested • EAL3 Methodically tested and checked • EAL4 Methodically designed, tested, and reviewed • EAL5 Semiformally designed and tested • EAL6 Semiformally verified design and tested • EAL7 Formally verified design and tested
The Common Criteria uses protection profiles in its evaluation process.
Elements:
ISO/IEC 15408 is the international standard that is used as the basis for the evaluation of security properties of products under the CC framework
https://resources.infosecinstitute.com/security-evaluation-models-cissp/#gref Initially, there were three Security Evaluation Models:
All the above three evaluation systems are to some extent obsolete or outdated and currently replaced by a more modern approach known as the Common Criteria model
In TCSEC, products are submitted to the National Computer Security Center (NCSC) and ultimately published in the Evaluation Product List (EPL). The act of rating a product's security capabilities is called the Trusted Products Evaluation Program(TPEP).
Certification is the comprehensive technical evaluation of the security components and their compliance for the purpose of accreditation. The goal of a certification process is to ensure that a system, product, or network is right for the customer’s purposes. Once certification has been passed, the results are submitted to senior management for the accreditation process.
Accreditation is the formal acceptance of the adequacy of a system’s overall security and functionality by management.
Certification is a technical review that assesses the security mechanisms and evaluates their effectiveness. Accreditation is management’s official acceptance of the information in the certification process findings.
Because software, systems, and environments continually change and evolve, the certification and accreditation should also continue to take place.
The verification process is similar to the certification process in that it validates security controls. Verification may go a step further by involving a third-party testing service and compiling results that may be trusted by many different organizations.
Completed by third party testing service. Results are trusted by most organizations.
Assurance is the degree of confidence that an organization has that its security controls are correctly implemented. It must be continually monitored and reverified.
机密性模型。 注意:注重机密性,此模型强调就是保证机密不能泄密。所以,机密程度越高,越保密,低的就不能读。写方面,高不能往低写,写的话机密的东西流到机密低的地方了。 所以他不允许数据由高级往低级流,但允许低级往高级流,机密性低的数据,跑到机密性高的地方,并不破坏机密性。
Properties
讲究完整性,不考虑机密问题。所以就颠倒过来了。你可以想象一下,完整性1,2,3,4级, 1级是最高完整性,也就是说我是最高指令,比如是董事会最高决议,它并不需要保密,谁都能看,但任何人不得破坏我的完整性,不能修改我的决议,只有我1级的人才能修改。所以2级的人不可以写我1级的内容。但2级可以读我1级的内容,来生成2级的信息。 此时,数据只能由高向低流,而禁止从低向高流。
Properties
Based on Bell-LaPadula Model Based on State Machine and Information Flow Model
Chosen-ciphertext attacks have the highest probability of the encryption being cracked compared to most other cryptanalysis attacks. In this type of attack, the intruder must capture a large portion of the ciphertext and then must be able to choose which parts of it are decrypted. That section of text is transformed into plaintext. The translation is then analyzed in an attempt to identify the key that was used in the encryption process.
A covert channel is a way of transmitting information using methods that were not originally intended for data transmission. 意図されてない通信経路を使う、組織のセキュリティポリシーを違反するチャンネル ・タイミングチャンネル( Timing channel):処理が実行されるタイミングを利用して意図されてない方法で情報を発信する ・ストレージチャンネル(Storage channel):保存されたデータの変更を利用して、と意図されてない方法で情報を発信する
The totality of protection mechanisms within a computer system, including hardware, firmware, and software, the combination responsible for enforcing a security policy.
Also, worth noting for your CISSP exam is that the TCB framework includes reference monitor, security domain and security kernel。
The CISSP exam outline mentioned the “security capabilities of information systems” and gave some technical examples such as memory protection, TPM, and cryptography. The security capabilities of information systems comprise not only technical means but also physical means and procedural means.
TCB is originated from Orange Book. The Trusted Computing Base (TCB) is a small subset of the system contained within the kernel that carries out critical system activities.
Security barriers and walls that surround sensitive areas should go from the true floor to the true ceiling. This means that the walls do not stop at a dropped ceiling or at the raised floor because those could be circumvented (回避,绕过) and used as entry points into the sensitive area.
The National Institute of Standards and Technology (NIST) standard pertaining to perimeter protection states that critical areas should be illuminated 8 feet high and use two foot-candles, which is a unit that represents the illumination power of an individual light. 照度単位は: Lux(ルクス)或いは Foot candle (1カンデラの点光源から全方向1フィートの面の照度の単位)。 英尺烛光(Foot-candle),字面意义是发光强度为1坎德拉的点光源的1英尺距离处的表面的照度。
These types of gases interfere with the chemical reactions in a fire and act as effective suppressing agents for class B and C fires. Halon is a gas that has been used in fire extinguishers for years and still exists in some older units. However, the EPA recently found that Halon is harmful to the ozone and potentially harmful to humans. Several replacement agents, including FM-200, are just as effective on fires as Halon and are being used in new units.
Halon is a type of gas used to interfere with the chemical reactions between the elements of a fire. A fire requires fuel, oxygen, high temperatures, and chemical reactions to burn properly. Different suppressant agents have been developed to attack each aspect of a fire:
Data center humidity should be maintained between 40% and 60%
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主要的EA框架有TOGAF、Zachman,EAP,FEA,DoDAF。目前主流的企业架构发展规划遵循两条路径,Zachman和TOGFA。由于TOGAF同时提供了一套架构方法,目前应用较为广泛,EA中有50%以上占有率。(TOGAF2009年调研报告)
它由美国国防部开发并提供了设计、实施和治理企业信息架构的方法。架构允许技术架构设计师从企业的不同视角(业务、数据、应用程序和技术)去理解企业,以确保开发出环境及组件所必需的技术,最终实现业务需求。
其核心就是如何从企业战略开始、以需求管理为核心,如何一步步制定业务架构、信息系统架构、技术架构、机会识别和解决方案制定、计划制定、实施管控、架构变更管理。
The CPU can function in one of four states:
Block算法的Mode
Online Certificate Status Protocol(OCSP)は、X.509公開鍵証明書の失効状態を取得するための通信プロトコルである。 RFC 6960 で規定されており、インターネット標準トラック上にある。
Certificate Pinningは,「証明書のピンどめ」と訳されたりしますが,「クライアントで許容するTLS証明書を予め規定しておく」ことを指します. Certificate Pinningを行うことで,「たとえ有効な証明書であっても見知らぬ証明書の通信は受け入れない」ようにすることが可能になります.
Crypto-shredding is the practice of 'deleting' data by deliberately deleting or overwriting the encryption keys.[1] This requires that the data have been encrypted. 密钥销毁是指主动覆盖或删除用于保护敏感数据的加密密钥,以保护敏感数据不被读取。对于审计应用程序或区块链这样不应该或不能删除历史记录的系统来说,密钥销毁技术对于隐私保护和GDPR合规非常有用。
信息刮取(Skimming)是一种高成本的攻击技术,但是因为操作简单,盗取信息的速度极快,而且部署起来十分隐蔽,所以特别危险。攻击者往ATM读卡器里插入恶意装置来盗取被刷卡片数据。垫片(Shimming)则是信息刮取(Skimming)的升级版,在终端读卡器里插入纸片般薄的装置就可以盗取芯片磁条复合卡的数据。 ATM skimming is when criminals place a device on the face of an ATM, which appears to be a part of the machine. It’s almost impossible for civilians to know the difference unless they have an eye for security, or the skimmer is of poor quality. When a skimming device is planted on an ATM, it gathers account data from any cards that are swiped. Those who planted it can then retrieve that data and put it on blank bank cards. Often, criminals will also hide a small pinhole camera in a brochure holder near the ATM in order to extract the victims' pin numbers. All of this allows them to access the funds in their victims' accounts.
When operating system patches are no longer available for mobile devices, the best option is typically to retire or replace the device.
Supervisory Control and Data Acquisition systems, or SCADA systems, provide a graphical interface to monitor industrial control systems (ICS)
アドレス空間配置のランダム化(英語: address space layout randomization, ASLR)とは、重要なデータ領域 の位置(通常、プロセスのアドレス空間における実行ファイルの基底とライブラリ、ヒープ、およびスタックの位置が含まれる)を無作為に配置するコンピュータセキュリティの技術である。
The noninterference model is loosely based on the information flow model. However, instead of being concerned about the flow of information, the noninterference model is concerned with how the actions of a subject at a higher security level affect the system state or the actions of a subject at a lower security level. Basically, the actions of subject A (high) should not affect the actions of subject B (low) or even be noticed by subject B.
they explain how outputs from one system relate to inputs to another system. Describes information flow between systems.
The feedback model of composition theory occurs when one system provides input for a second system and then the second system provides input for the first system. This is a specialized case of the cascading model Example: HTTP Request and Response A -> B : Request A <- B : Response
Input for one system comes from the output of another system. Example: Web server with database backend A -> B -> C : Chaining
One system sends input to another system but also sends input to external entities. Example: CC and BCC in email A -> B : To Destination A -> C : To Hookup
Simply put, process confinement allows a process to read from and write to only certain memory locations and resources. This is also known as sandboxing.
The bounds of a process consist of limits set on the memory addresses and resources it can access.
More secure systems may require physically bounded processes. Physical bounds require each bounded process to run in an area of memory that is physically separated from other bounded processes, not just logically bounded in the same memory space. Physically bounded memory can be very expensive, but it’s also more secure than logical bounds.
Process isolation ensures that any behavior will affect only the memory and resources associated with the isolated process. Isolation is used to protect the operating environment.
Isolation is best described as confining a process by implementing access bounds to ensure compliance to a set of predetermined access criteria such that its execution, failure or compromise does not affect other process. The three terms, isolation, bounds and confinement are inter-related. Confinement basically means ensuring that the process only reads and writes to specific resources (such as memory), whereas bounds refer to the authority level attached to the process which defines the specific resources it can access such as memory locations. Isolation is the concept whereby confinement is implemented using bounds.
Notes
One which protects data for many types of users
Degree of confidence in satisfaction of security needs Needs to be maintained Changes decrease assurance, hences, reevaluation is needed
In the Fair Cryptosystem approach to key escrow, the secret keys used in communications are divided into two or more pieces, each of which is given to an independent third party.
an M of N control the M stands for minimum and the N stands for total number and in this case you need 5 people to gain access to the system that 10 people have a key to. It’s a way to ensure that only one person doesn’t have access to any given system.
Another example: What if 5 people have combined keys to a bank vault. That makes the N = 5. Now let’s say you need 2 of those 5 people to come together to gain access to that vault. That’s the M, i.e. 2, the minimum number of people needed to get in.
Requirements
A security clearance is a status granted to individuals allowing them access to classified information (state or organizational secrets) or to restricted areas, after completion of a thorough background check. 秘密にすべき情報を扱う職員に対して、その適格性を確認すること。
Blowfish allows the user to select any key length between 32 and 448 bits.
bcrypt 用到了blowfish技术. bcrypt的一个非常重要的特征就是自适应性,可以保证加密的速度在一个特定的范围内,即使计算机的运算能力非常高,可以通过增加迭代次数的方式,使得加密速度变慢,从而可以抵御暴力搜索攻击。
Provos和Mazières利用了这一点,并将其进一步发展。他们为Blowfish开发了一种新的密钥设置算法,将由此产生的密码称为 “Eksblowfish”(”expensive key schedule Blowfish”)。这是对Blowfish的改进算法,在bcrypt的初始密钥设置中,salt 和 password 都被用来设置子密钥。然后经过一轮轮的标准Blowfish算法,通过交替使用salt 和 password作为key,每一轮都依赖上一轮子密钥的状态。虽然从理论上来说,bcrypt算法的强度并不比blowfish更好,但是因为在bcrpyt中重置key的轮数是可以配置的,所以可以通过增加轮数来更好的抵御暴力攻击。 https://zhuanlan.zhihu.com/p/410896683 https://zhuanlan.zhihu.com/p/400196101 上图是一个bcrypt哈希结构的示例图,其由四部分组成: Prefix说明了使用的bcrypt的版本 Cost是进行哈希的次数-数字越大生成bcrypt的速度越慢,成本越大。同样也意味着如果密码库被盗,攻击者想通过暴力破解的方法猜测出用户密码的成本变得越昂贵。 Salt是添加到要进行哈希的字符串中的随机字符(21.25个字符),所以使用bcrypt时不需要我们在表里单独存储Salt。 Hashed Text是明文字符串最终被bcrypt应用这些设置哈希后的哈希文本。
There are a total of four such rules:
CPTED(Crime Prevention Through Environmental Design)
MAC: message authentication code. MAC是通过MAC算法+密钥+要加密的信息一起计算得出的。 同hash算法(消息摘要)相比,消息摘要只能保证消息的完整性,即该消息摘要B是这个消息A生成的。而MAC算法能够保证消息的正确性,即判断确实发的是消息A而不是消息C。 同公私钥体系相比,因为MAC的密钥在发送方和接收方是一样的,所以发送方和接收方都可以来生成MAC,而公私钥体系因为将公钥和私钥分开,所以增加了不可抵赖性。
hmac主要应用在身份验证中,如下是它的使用过程:
In cryptography, a key derivation function (KDF) is a cryptographic hash function that derives one or more secret keys from a secret value such as a main key, a password or a passphrase using a pseudorandom function (伪随机函数).
KDF是hash函数,通常用来将短密码变成长密码 KDF是密码学安全的,详见(实用密码学工具——Hash) KDF需要加salt,用于防彩虹表,salt长度至少要大于hash长度 KDF需要有能力消耗大量计算资源,用于防暴力破解
Multi-processing is the multi-tasking capability fulfilled through a multi-processor system.
物理メモリを共有して管理する「メモリ共有型並列コンピューティング(マルチプロセッシング)方式」のこと。全てのCPUに対して対称的、均一的に処理が割り付けられた複数プロセッサによる並列処理方式のことを言う。
搭載された個々のCPUのそれぞれに別々な命令を割り当てる方法のことである。 たとえばひとつのCPUにはOSの制御を行わせ、またもうひとつのCPUにはアプリケーションの演算をさせる、といった方法がASMPに相当する。
Single-state systems are designed and implemented to handle one security level of information.
multistate systems/processors can simultaneously operate at multiple security levels (i.e. TS, Secret, Unclass.)
function that loads and executes a new child process.
Forking: when a process forks, it creates a copy of itself. The original process that calls fork() is the parent process, and the newly created process is the child process. Both processes return from the system call and execute the next instruction.
Fork is the default on Linux (it isn't available on Windows), while Windows and MacOS use spawn by default. When a process is forked the child process inherits all the same variables in the same state as they were in the parent.
可屏蔽中断(maskable interrupt): 可通过设定中断屏蔽寄存器EFLAGS中IF标志位关闭的中断 不可屏蔽中断(non-maskable interrupt, NMI): 无法通过设置标志位屏蔽的中断,如电源掉电、时钟中断
The security perimeter is a boundary between items that are within the TCB and items that are outside the TCB.
The security kernel is a portion of the operating system’s kernel and enforces the rules outlined in the reference monitor. It is the enforcer of the rules and is invoked each time a subject makes a request to access an object. 安全内核(Security Kernel)是实现引用监控器的TCB组件集合。
Reference monitor(引用监控器): defines a set of design requirements on a reference validation mechanism, which enforces an access control policy over subjects' ability to perform operations. 引用监控器:位于主体和客体之间,用于验证和访问控制。
ALU (arithmetic logic unit):performs mathematical functions and logical operations on data.
General registers: used to hold variables and temporary results as the ALU works through its execution steps.
Special registers (dedicated registers) : hold information such as the program counter, stack pointer, and program status word (PSW).
The program counter register: contains the memory address of the next instruction to be fetched。
program status word (PSW) holds different condition bits. One of the bits indicates whether the CPU should be working in user mode (also called problem state) or privileged mode (also called kernel or supervisor mode).
CVE (Common Vulnerabilities and Exposures)は、 情報セキュリティにおける脆弱性やインシデントについて、それぞれ固有の名前や番号を付与し、 リスト化した事典です。
CVEが登場するまでは、各種製品ベンダーやセキュリティベンダーが、 脆弱性に対して独自に名前を付けていたため、各ベンダーが公表する脆弱性情報はばらばらで、 ある脆弱性情報が同じ問題についてのものなのかどうか、はっきり判別することは困難でした。 さらに、脆弱性のデータベースや対応ツールの相互互換性も、有効性に乏しいことになっていました。
そのような状況を改善するため、 米国政府の支援を受けた非営利団体のMitre Corporation (マイターコーポレーション)が、 1999年に脆弱性を一意に特定できるようCVEを提案・実装しました。 このCVEの登場によって、脆弱性の一つ一つに固有の名前、 およびCVE IDと呼ばれる固有の番号が付与されるようになりました。 その結果、ベンダーをまたいだ脆弱性情報の比較が、容易に行えるようになりました。
– Proactive ⇒ predict the future ⇒ hard。 Proactive cybersecurity is what you do before an attack. – Reactive ⇒ learn from the past ⇒ easier