(outline as of 9/13/2015)

Course Title:Cryptography

Section 1-1 Topic:Introduction To Cryptography

Learning Objectives:This introduction video provides an outline of the curriculum covered in Cybrary's in-depth Cryptography course.

Confidentiality, Integrity, Availability and Authentication

How companies use cryptography

How penetration testers can also use cryptography

Tools, Techniques and Attacks

Academics discusses history of encryption.

Academics simply encrypt or hash, why aren't people using hashing more?

Professional is just, encrypt or not, hash or just verify

Section 1-2 Topic:Key Concepts of Cryptography:PKIS & Encryption

Learning Objectives:Cryptography is one of the most underrated courses of study in the industry. Of those who do study it, issues with comprehension tend to hinder individual mastery. By taking this course, learners will finally be able to grasp all the critical concepts, theories and practices associated with Cryptography.

This Cryptography presentation discusses and demonstrates the key concepts of Cryptography from attacks, PKIs and Encryption in detail.

You’ll learn about the difference between public and private keys and about the similarities and differences between symmetry & asymmetry. We’ll also discuss the concept of integrity and confidentiality and their relationships to/with protocols.

This Cybrary Cryptography course will help you master the basics of Cryptography as you begin to develop the discipline needed to become an accomplished pen tester.

Keys and Principles

1.       Keys

1a. Symmetric - also referred to as same keys, private key, symmetric key - same (confidentially)

Different Version/Ways/Procedures to get PlainText to CipherText

Symmetric Cipher Examples:

AES, DES, 3DES, IDEA, CAST, twofish, Blowfish, RC2, Serpent, Rijndael - (there are others, chart at end of section)

PGP, OTP (One Time password)

Mnemonic device to remember some Symmetric Ciphers (how it reads, sounds and then corresponds, in English):

Hey! These 3 guys, had an idea to cast their rod to fish for blowfish, but instead received, serpents in the rain.

A! Dees 3 guys, had an IDEA to CAST their rod TWOFISH for BLOWFISH, but instead Received, Serpents in the Rain.

AES DES 3DES                 IDEA      CAST                 TWOFISH        BLOWFISH                       RC2           Serpent          Rijndael

1b. Asymmetric - public/private key pair - what one key does, the other key undoes

(confidentially, authentication, nonrepudiation)

Asymmetric Cipher Examples:

DH (key exchange), El Gamal (open source), RSA (internet), Elliptical Curve (for limited processor machines),

Knapsack, DSA (popular as a US standard)

Mnemonic device to remember some Asymmetric Ciphers (how it reads and then corresponds, in English):


Diffie Hellman, El Gamal, RSA, Elliptical Curve, Knapsack, DSA

2.       Principles (C, I, A)

Principles of CIA (confidentiality, integrity and authentication) along with PAIN will be discussed in detail later, focus on concepts and definitions.

Substitution/Transposition - PlainText to CipherText, and CipherText to PlainText

Disk Encryption (further detail later)


Detect unauthorized change via output of Message Digest, also known as, a hash.

MD5 (128bit), SHA (160 bit, also variable), Hashing Calculator


A public key infrastructure (PKI) is a set of hardware, software, people, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates and manage public-key encryption.

CA, RA, X.509

IKE (internet Key exchange), ISAKMP, CRL (certification revocation list), OCSP (dynamic, checks x.509 cerrtification)


Known Plaintext

Known CipherText

Chosen CipherText (needs physical access to machine)

Chosen Plaintext (choose what gets decrypted, needs physical access to)


SSH (replaced Telnet)

HTTPS (SSL/TLS with security protocol, wraps all upper layer application in cryptographic wrapper)

IPSec (Network Layer, analogy truck:authentication header/integrity check, payload:integrity check and confidentiality check)

SSL/TLS (protocols)

Section 1-3 Topic:Introduction to Cryptographic Tools

Section 1-4 Topic:Services & Threats of Cryptography

Section 2-1 Topic:Integrity Checking:Modifications

Learning Objectives:These videos, while separate, build on each other and are all linked.

Explain how cryptography is used to protect CIA.  ‘CIA’ can also be a ‘PAIN’ – all defined…

1. Confidentiality (C of CIA) (also Privacy, P of PAIN) - prevent unauthorized disclosure of data


a. Social Engineering:Opening Unsigned Emails (Spear Phishing, Whaling Attack)

Defense Controls:Physical, Technical, Mail Filter, Administrative Training

Ideas:Separation of Duties, Need to Know

b. Media Reuse:USB Thumb Drive reuse is common.

Sanitizing can also be referred to as Zero'ing

Destroying a hard drive, completely, requires incineration.

Degaussing method only works for Magnetic Media.

Deleting only removes pointer to file and Formatting can be recovered.

c. Eavesdropping:protocol (packet) analyzer/ sniffer. Wireshark is popular.

Replay Attack:Capturing a packet that contains a password and reusing;

This allows access to ‘use’ a password without never knowing the actual password

Zero Knowledge Proof:Kerberos allows end user to prove the password, without sending

               password across network

Hack Attack Discussion:Directory Services:Query DNS, reply to send Credential to Server 1

2. Integrity (I of CIA, I of PAIN)

Accidental Modifications are checked by message digests, or hashes.

(digital representation of file - checks if identical)

Intentional (Malicious) Modification can be checked by using:

Message Authentication Code (MAC) or

Digital Signatures (both provide an extra step of authentication)

3. Authenticity (A of CIA, A of PAIN)

How to prove is truly came from the sender, is it valid?

4. Non repudiation (N of PAIN)

Combination of Integrity and Authenticity – must have both!

Sender can't dispute sending the message or contents - we use digital signatures for this

(further detailed explanations will follow on how)

Mnemonic Device, some remember it as CIA, or PAIN - P(rivacy) A(uthentication) I(ntegrity) N(on Repudiation)

 Section 2-2 Topic:CipherText

Learning Objectives:Learn how to properly create CipherText and the processes behind it in this lecture series on Cryptography.


Plaintext + Initialization Vector + Algorithm + Key = CipherText

Plaintext is just plain, non-encrypted text or data.

Initialization Vector (IV) adds randomness and complexity.  Randomized Starting Point

~Computer cannot generate a random number, so we have a pseudo random number.

~We could take any number of variable pieces of data to generate a pseudo random number such as:

A Date:12/12/1999 would be 34.

Algorithm (aka Cipher, is a collection of math functions)

               ~Symmetric Cryptography can also be referred to as:

                               Private Key

                               Secret Key

                               Session Key

                               Shared Key (i.e. shared between two parties)

               ~Any Symmetric Algorithm, to be discussed later, will be either:




                               Discrete logarithms


Key (Crypto Variable) is the instruction on how to use the algorithm (how to use the math)

Section 2-3 Topic:Master Pattern Analysis with CrypTool

Learning Objectives:Learn how to perform pattern analysis with CryptTool to identify trends during the encryption process.

CrypTool Lab

CrypTool is a non-academic analysis tool that offers a fundamental understanding of encryption algorithms.

Can be found at:https://www.cryptool.org

Section 2-4 Topic:Symmetric Encryption

Learning Objectives:The Symmetric Encryption discussion opens by reviewing the usage of random numbers, explaining what Replay Attack is, the importance of unique information on data packets and in sequencing and defining key terms including Nonce and Key Generation.

Then, you’re introduced to Symmetric Encryption with a basic summary of how it works, what ciphers are, the different types of Symmetric Ciphers, what happens with block ciphers, and what the difference means to encryption and decryption as a process.

As a penetration tester, you must know the difference between confusion and diffusion.  You’ll observe how that correlates to how algorithms work and the importance of strong math in configuring algorithms.  And you’ll learn what happens as algorithms are used and what you need to look for in your testing results.

Cryptographic Uses of Random Numbers

               ~There is very little true randomness (or entropy) so instead we use pseudo random.

               Nonces - process of stamping uniqueness on packet without being sequential.

                               Note:Adds uniqueness and helps to stop replay attacks

               Key Generation - keys must be unique, (pseudo) random and of a suitable length

                               Note:All things being equal, longer will offer more protection.

Symmetric Encryption (same key on both ends - real world example:a house key)


                               Confusion - Confusion relates to complex math and substitution

                               Diffusion - Diffusion relates to permutations or rounds

                               (DES went through 16 rounds, 3DES goes through 48 times/rounds/permutations)

                                Bit length is not necessarily the final determination of the strength of a key.

                               Open - Kerckhoffs Principles, algorithm should be open

                               Key Generation – (definition above)

Example Algorithm:

[R1]+2, [R2]-2, [R3]*2, [R4]/2, ... [R6]^2 - each [R] would be considered an SBox (or substitution box)

                Block Ciphers (slower, but more secure)




                               3DES (secure, very process intensive, but AES would be preferred)

                               AES (Advanced Encryption Standard)

Section 2-5 Topic:Stream Ciphers, XOR and RC4

Learning Objectives:As a continuation of learning about Symmetric Encryption, this lesson explores the other type of cipher:Stream Ciphers.

We’ll go much deeper into what happens during XOR (which stands for exclusive Or), what transposition and substitution is, and whether or not multiple transposition and substitution is preferred. You’ll also observe a rich demonstration of how XOR provides encryption, learn what RC4 is and what takes place at the encryption and decryption level.

As a Penetration Tester, you must understand the key functions of each of these events, what their impact is on each other and how to determine when to use one over another in Symmetric Encryption.


               One bit at a time

                               Transposition (THE becomes HET; moving over 1 character)

                               Substitution (A for T, B for H, C for E, assigning different characters, etc.),

               XOR (Exclusive Or)

                               How XOR works, since it is a stream, it goes bit by bit

                               XOR Example

                               A real world example could be WEP/WPA which uses RC4

                                               (fast encryption and decryption, trades security for speed)

                               WPA2 uses AES which is more secure.

Section 2-6 Topic:Pros and Cons of Symmetric Cryptography

Learning Objectives:As we wrap up our lesson on Symmetric Cryptography, we must address the pros and cons of this encryption method.

You’ll discuss its greatest pro—speed. But as we know, sometimes being too fast occurs at a cost. Those costs will be discussed when we cover the cons of Symmetric Cryptography, such as Out of Band Key Distribution, lack of authenticity, issues with integrity, and non-repudiation.

Knowing what the boundaries are with your encryption resources will enable you to make accurate decisions and advise decision-makers with specific points of fact.


               Out of band key distribution (no straight forward means of key exchange)

               Not Scalable (every unique conversation requires a key)

               No 'A'uthenticity (no court room authenticity, both parties share the key)

               No 'I'ntegrity (corruption happens, it cannot detect corruption or packet drops)

               No 'N'on Repudiation (requires both Authenticity and Integrity)


               Does provide 'P'(rivacy/Confidentiality) of 'PAIN'

               FAST, FAST, FAST! (It can be noticably real world faster)

Section 2-7 Topic:Public Key Cryptography

Learning Objectives:This final lesson in Section 2 of the Cryptography module focuses on public key cryptography.

Every user on the network is given a public and private key for encryption. This lesson discusses how the public and private key exchange happens, how Asymmetric Cryptography works, what has to happen so that public and private key exchanges can authenticate, and what the advantage/disadvantages are to employing Asymmetric Cryptography.

And finally, there is a contrast discussion on Symmetric vs. Asymmetric Cryptography discussion introducing how penetration testers can get the best out of both worlds.

Public Key Cryptography

               Two keys issued to each user (simplified example)

                               ~1 public key and 1 private key (a key pair)

                               Done automatically at the application layer with Outlook, Browser, etc.

               Anything encrypted with one key (public) can only be decrypted with the other (private) and vice versa

               Provides key exchange, scalability and non-repediation


Section 3-1 Topic:Asymmetric Cryptography Functions

Learning Objectives:As we wrap up our lesson on Cryptography, we spend our last section exploring Asymmetric Cryptography in detail with several labs to supplement the lecture knowledge.

A penetration tester must be able to understand what happens at each stage of encryption/decryption phase and how those transactions affect or trigger the outcomes of other events.

In this session, we learn how Asymmetric Cryptography delivers all four encryption services:privacy, authenticity, integrity, non-repudiation (PAIN). We’ll then we find out what happens at each state of asymmetric cryptography.

At the conclusion of this lesson, you’ll know what info is exchanged between public and private key, how packet verification occurs, how a hash is created and how hashing algorithms are used.

Asymetric Cryptography P.A.I.N.


               Sender always encrypt with the receiver's PUBLIC key.

               Receiver decrypts with receiver's PRIVATE key which only that receiver has.


               Sender will encrypt \"something\" with the sender's PRIVATE key.

               When the receiver is able to successfully decrypt that 'something' with that sender's PUBLIC key,                                                   that proves it was encrypted with the sender's PRIVATE key, which only the sender has.

                Example:I am sending message; my content is encrypted with receiver’s public key.

                               The time stamp is encrypted with senders (my) private key - this can prove that *I* sent it.


               Create a message digest (hash) with a hashing algorithm

                               (MD5:128 bit; used less, SHA-1:160 bit; used less, SHA 256:256 bit)

               Asymmetric and Symmetric both use keys

               Hashes do not use keys, they only use math functions

                Example:Very rudimentary, but concept is important - hashes are one way functions

                               H E L   L    O           (every characters numeric value, or the message, then added together)

                               8 5 12 12 15 = 52                (this value is the message digest/hash)

               If you ONLY know the 52 (hash), trying to figure out the corresponding additive values would be arduous.    Coupled with higher bit level encryption, the effort could take longer than we have time in the universe.

                However, if they both match, the message has not been modified.  Very easy one way math.


               Sender encrypts hash with the sender’s private key. Receiver decrypts hash with sender’s public key.           Receiver hashes document - if hashes match, receiver gets a guaranteed message has not been modified.                  This is called a digital signature.


*It is generally accepted that you cannot reverse a hash*

                SSL - secure sockets layer – Asymmetrical (for all above), Symmetrical for data exchange (speed)

Section 3-2 Topic:Public Key Exchange

Learning Objectives:we continue our focus on Asymmetric Cryptography with a detailed diagram and discussion on secure public key exchange and how it works. You’ll learn the entire process from start to finish and why it’s a faster, more reliable encryption process.

You’ll also learn about Certificates of Authority (CA), what comprises the certificate revocation list (CRL), what a online certification status protocol (OCSP) is, and why they are each essential to the encryption process. We’ll discuss the entire PKI (public key infrastructure) and what role each of its components has.

And finally, we’ll observe then explore what CA hashing looks like during encryption and decryption at the browser level, and learn why thorough PKI knowledge and training in Symmetric & Asymmetric Encryption for netadmins and cyber security professionals is essential.



[Desktop clients] -> uses https:// to reach -> [BofA servers]

               1. Client requests via https to server

               2. BofA sends public key* to client key

               3. Client generates a symmetric session key (i.e. 8439...)

                               how does it get this session key to server?*

               4. Client encrypts the session key with servers public key

                               (since server will be able to decode with private key)

               Result:Enables Asymmetric Key Exchange/Symmetric Data Exchange - Secure Channel Setup

*This model still allows Man In The Middle (MITM) attacks, we must go further for assurance and authenticity.

               To cure this, we must have the following public key being verified by a CA via public key infrastructure

               BofA server proves to Verisign CA (certificate of authority) that they are truly BofA

                               (other CA’s would be Thawte, Baltimore, Entrust, etc.)

               The CA then gives a certificate back to bind public/private key to server

*How do we know it came from Verisign, a trusted authority?

               Verisign sends certificate with private key (can be decrypted with Verisigns public key).

*Your web browser may be pre-loaded with CA's - trust gained by having CA's public key.

Could set up our own CA, where we 'vouch' for ourselves.  While that may not work for web based transactions, but for internal network transactions, it may be an acceptable trade-off.

CRL (pronounced krill) - Certificate Revocation List

OCSP - Online Certificate Status Protocol

Section 3-3 Topic:Advanced Encryption Package

Learning Objectives:The Advanced Encryption Package lab demonstrates use of an advanced encryption analysis components and how to use them to dig deeper in your file, password and data analysis.

You’ll observe creation of a password protected text file, see how the Advanced Encryption Package tool rates the strength of assigned password, and uses powerful algorithms to generate secure encryption for network files and directories.

In the Advanced Encryption Package lab, you’ll learn the advantages and disadvantages in the integrity principle vs. confidentiality principle and how those differences impact Symmetric vs. Asymmetric encryption. You’ll also see how to perform secure deletions, and learn how to use this tool as a key generator and PKI manager.

Advanced Encryption Package Lab

Can be found (Free Trial) at: http://www.aeppro.com/

Section 3-4 Topic:Hashing and Hash Collisions

Learning Objectives:This session of our Cryptography module introduces an extensive overview on Hashing. It begins with mapping out exactly what a Hash does and where it falls short and why it’s a disadvantage being one-directional.

You’ll also explore Hash collisions—what they are, how they happen, what it takes to recreate them, what happens when there is no integrity and how that is determined by the penetration tester.


               Hash functions

                               Scenario 1:A MITM could just intercept and change the hash!

                                               Without authenticity, hash is only useful for detecting accidental changes/corruption.

                               Scenario 2:Digital Signature adds authentication to the integrity, we get true non repudiation:                                                       protects against accidental or intentional changes...this all requires a PKI ($ overhead)

                               Scenario 3:Introduce a solution; use a

                                               M(essage)A(uthentication)C(ode) = Message + Symmetric Key + Hashing Algorithm

                                               (this would be a step below having/paying for the PKI overhead)

               Passwords, credit cards, PII

               Digital Forensics

                               Hash the drive before doing forensic analysis (write protect the drive).

                               Even opening a file could change the hash.

               Malware analysis and virus detection

               Hash Collisions

                               Two different pieces of text product the same hash.  Collision resistant hashes are the goal.

                               If a collision is achieved, you now can produce the hash even though it was not the original.



Section 3-5 Topic:Hash Calc

Learning Objectives:The Hash Calc lab teaches you what  information is gained from using Hash Calculators to analyze files within a directory, or specifically targeted files. For example, the output of the Hash Calc tool includes the message digest about the target as well as all its relevant integrity algorithms.

The lab also discloses several integrity algorithms not output from the Hash Calc tool that provide a wider range of output datasets. Used in conjunction with the Hash My Files, and Advanced Encryption Package tool Hash Calc can be a very revealing “go-to” suite of resources for cryptographic analysis.

HashCalc  is a fast and easy-to-use calculator that allows to compute message digests, checksums and HMACs for files, as well as for text and hex strings. It offers a choice of 13 of the most popular hash and checksum algorithms for calculations.

Can be found at:http://www.slavasoft.com/hashcalc/

Section 3-6 Topic:Digital Signature, SHA2(256) and RSA

Learning Objectives:In this sub-part of our previous Hash lesson, we take a closer, more intimate look at digital signatures, SHA2(256). We’ll look at Asymmetric Algorithm, RSA, what is met by satisfying the digital signature standard, and what the entire packet transfer looks like when hashing takes place.

We will also introduce concepts behind protecting data at rest.

Several key definitions are discussed included full disk encryption, file encryption, code signing with a discussion on how they differ, what occurs in each of those data transactions, and why that sequence of events is important for Penetration Testers to know as part of the Asymmetric encryption process.

Digital Signatures

               Hash (remember, hashes are just one way math)

                               MD4, SHA-1, SHA-2

               Asymmetric Algorithm

                               RSA - satisfied the Digital Signature Standard

Protecting Data At Rest

               File Encryption - some files or properties may be readable if hard drive is moved to another computer OS                                   (i.e. Windows Hard Drive using Encrypting File System is physically moved to a Linux Box)

               Full Disk Encryption - modern motherboard have TPM (trusted platform module)

                               BitLocker, PGP, etc. achieve this.

               Code Signing - distributed code accessed on Internet (Java, Javascript, ActiveX) should be digitally signed.

Section 3-7 Topic:

Hash My Files

Learning Objectives:

This lab demonstrates the Hash My Files tool which analyzes files by specific file or by directory and validates their integrity. The Hash My Files process report is basic and the output can be exported to a series of different formats including HTML.

You’ll also observe a demonstration of how the Hash My Files tool works and what you can learn from the information it provides.

Because of their strong algorithms, security professionals rely heavily on hashing as a reliable Cryptographic analysis tool for integrity validation.

HashMyFiles tool analyzes files by specific file or by directory and validates their integrity.

HashMyFiles is small utility that allows you to calculate the MD5 and SHA1 hashes of one or more files in your system. You can easily copy the MD5/SHA1 hashes list into the clipboard, or save them into text/html/xml file.

HashMyFiles can also be launched from the context menu of Windows Explorer, and display the MD5/SHA1 hashes of the selected file or folder.

Can be found at:


Tools Used

CrypTool - http://www.cryptool.org

Advanced Encryption Package - http://www.aeppro.com

HashCalc - http://www.slavasoft.com/hashcalc/

HashMyFiles - http://www.nirsoft.net/

(links cannot be guaranteed, as they are maintained independently)


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