Week 2-Summarize the Basics of Cryptographic Concepts Flashcards
1
Q
Is the set of all possible keys that can be used in an encryption algorithm. (i.e. 56-bits=2^56, 256-bits=2^256 and 512-bits=2^512).
A
Keyspace
2
Q
Is the process of changing the values. Complex substitution functions are used to create___
A
Confusion
3
Q
The process of transforming plaintext (i.e. unencrypted data) into cipher text (i.e. encrypted data) using an algorithm and a secret key.
*The goal of ___ is confidentiality
A
Encryption
4
Q
Is a measure of ensuring the:
*Authenticity
*Integrity
*Non-repudiation
of a digital document or message
A
Digital Signature
5
Q
___means that the use of the algorithm & key length is allowed, but the user must accept some risk (weakness)
A
Deprecated
6
Q
Is a process converting input data of arbitrary length into a fixed-sized output.
Known as a __value, digest or fingerprint
A
Hashing
7
Q
Term used in cryptography to refer to a secret value used as a key, seed or initialization vector in an encryption or decryption algorithm.
Is a critical component of a cryptographic system, as it is used to transform plaintext & data into cyphertext or to decrypt ciphertext back to plaintext, the strength and security of the depends on its lenth, randomness and secrecy
A
Cryptovariable
8
Q
The process of changing the order, sending bits through multiple rounds of transpositon is used to create___
A
Diffusion
9
Q
Malicious code embedded in advertising
A
Malvertising
10
Q
Hiding method:
modifying color space of a PNG image
Purpose:
hiding malicious code within a banner ad
A
Hiding method:
Malicious steganography
Purpose:
Segano
11
Q
Hiding method:
Data hiding in HTML comment tags of the HTTP 404 error page
Purpose:
Embedding command and control commands
A
Hiding method:
Malicious seganography
Purpose:
Teslacrypt
12
Q
Common symmetric encryption algorithms
A
3DES
AES
13
Q
Common Asymmetric encryption algorithms
A
RSA, ECC, Difie-Hellman
14
Q
__uses the same cryptographic key to encrypt and decrypt data.
*it is computationally efficient and can process large blocks of data.
*The disadvantages are key distribution and scalability
A
Symmetric encryption
15
Q
__uses a pair of mathematically related keys.
*a private key and a public key.
*requires a lot of processing power and is slower.
*More suited for small blocks of data.
*advantage is scalability
A
Asymmetric encryption
16
Q
_used to prove integrity
_produces a unique one-way fixed length
_representation of data set know as a __ , digest, checksum or fingerprint
_digests are compared and if they are the same then there is assurance that the data has not been modified
A
hash
17
Q
Hash common algorithms are:
A
MDx
SHAx
18
Q
__is used to prove authenticity of the message and verify the sender’s identy.
*A _ is a message digest encrypted with the sender’s private key.
A
Digital Signature
19
Q
_are the mechanism used to generate a private key and to associate a public key with a collection of components sufficient to authenticate the claimed owner.
*The certificate is issued by a trusted certification authority, a web of trust, or self-generated and self-signed.
*is a unique ID for users, devices, applications and services.
A
Digital certificate
20
Q
The cryptographic component used to ensure confidentiality.
A
Encryption
21
Q
The cryptographic component used to prove integrity.
A
Hashing
22
Q
The cryptographic component used to prove authenticity.
A
Digital signature
23
Q
The number of keys used in asymmetric encryption
A
Two (public and private)
24
Q
The key that is used to create a digital signature
A
the senders Private Key.
25
**Security-In-Action**
1) Your organization plans to begin digitally signing messages to prove authenticity.
2) You have been asked to eplain to the user community what the purpose of a digital signature is and how it works.
3) What do you tell them
A digital signature is used to verify (prove) that the message actually came from the sender and that it has not been modified in transmission.
*On behalf of the user, their messageing program will sign the message with a private key that is specific to the user.
***Technical details**
The original message is hashed and a message digest is created. The message digest is encrypted with the senders private key. The recipient decrypts the message digest with the senders public key to validate the sender. The recipient also hashes the original message and compares the two message digests to validate that the message was not modified in transmission.
26
**Common Certificate properties**
***Thumbprint**-Hash of the certificate (unique identifier)
*Subject-name of the certificate. (DN,CN, O, OU)
***Issuer**-the entity that issued the certificate.
***SAN**-Additional information about the subject.
***Key Usage**- What the certificate can be used for.
***Version-X.509** certificate version
***Valid From/To-Date **range in which the certificate is valid.
***CRL distribution**-Location of the certificate revocation list
***Public key-**Public key
***Algorithm**-Algorithm used to sign the certificate.
27
**Certificate Formats**
***PEM-**most common certificate format. Can include both the certificate and private key in one file or can be a separate file. Extensions include .pem, .crt, .cer, .key.
***Der-Binary** form of a PEM. Extensions include .cer, .der.
***P7B/PKCS#7-**Contains certificate but not the private key (Base64 encoded ASCII). Extensions include .p7b, .p7c.
***PFX/PKCS#12**-contains certificate, intermediate certificate and private key (binary). Extensions include .pfx, .12
28
**Types of Digital Certificates**
***Personal**-Verifies a user identity (generally used for email).
***Machine**-Verifies a device identity.
***Domain**-Verifies a domain (wildcards for subdomains)
*Organization-Verifies a domain and an organization.
***Extended Validation**-Verifies a domain and an organization subject to additional standardized global verification processes.
***Code/Object signing**-Verifies origination/ownership as well as object integrity.
***Trusted/Intermediate-**Identifies root and intermediate Certificate Authorities.
29
**Certificate Pinning**
Forces a client application to validate the server's certificate against a known copy.
*pinning can be preloaded into the application, or it can automatically pin whatever certificate the server sends during the first client-to-server call.
*preloading protects the application, as an attacker might be able to pin their own certificate upon the first call.
***Use case***
Pinning is intended to add a layer of security against a Man-in-the -Middle attack.
30
# Security-In-Action Certificate Assurance
Your organization is planning on launching a customer facing website. It is very important that customers feel confident bout the trustworthiness of the site.
You have been asked which certificate is better-Domain Validation, Organizational validation, or Extended validation-and why?
What is your response
Response:
*Domain validation* only requires that the website owner demonstrate control over the domain.
*Organizational validation* documents information about the site operator but the user needs to open the certificate to see the datails.
**Extended validation***requires that an organization demonstrate exclusive rights to use a domain, confirm its legal, operational and physical existence, and prove that the entity has authorized the issuance of the certificate. **Clicking on the padlock will reveal that the certificate is EV. Unfortunately the "green bar" is no longer in use.
| Answer is Extended validation
31
Trused Certificate Phases
**Enrollment**-Enrollment initiated by users request to a Certificate Authority.
**Validation**-When a certificate is used, that status is checked to verify that it tis still operationally valid.
**Suspension**-Temporary revocation of a certificate until a certificate problem can be resolved.
**Revocation**-Permanent withdrawl of trust by issuing authority before scheduled expiration date.
**Renewal**-Prior to a certificate reaching its expiration date, it must be renewd
**Destruction**-When a certificate is no longer in use (expired or revoked), the certificate and backup copies should be destroyed along with the associated private key.
32
Enrollment-Certificate Authority (CA)
Digital certificates are issued by commercial trusted parties, called Certificate Authorities (CA).
* *Browsers and devices trust a CA by accepting the Root Certificate into its root store-essentially a database of approved CAs that come pre-installed with the browser or device.*
* *CAs use these pre-installed Root Certificates to issue Intermediate Root Certificates and entity Digital Certificates.*
*the CA receives certificate requests, validates the applications, issues the certificates, and publishes the ongoing validity status of issued certificates.
33
Registration Authority
A Registration Authority (RA) offloads some of the work from the CA.
* The RA can accept and process registration requests and distrubute certificates.
* A Local Registration Authority (LRA) requires physical identification. (rare occasion, must go to office to prove validity).
34
Certificate Request Process
1). Applicant generates a public/private key.
2). Applicant submits certificate request (Identifying info + public key)
3). The CA (or RA) validates identity of the applicant.
4). The CA generates a certificate and signs it with their private key.
5). The CA (or RA) sends the certificate to the applicant.
35
Enrollment Self-generated certificate
Digital certificates can be self-generated and self-signed.
*Problems with self-generated/signed
1. A self-signed certificate can be easily impersonated.
2. Presents warning message when used.
3. Cannot be revoked.
Use Case:
Internal development
NOTE:
Self-generated certificates can be signed and validated by other users-referred to as *web of trust*.
36
Certificate Validity
**Certificate Revocation List (CRL)**-CA maintained list of certificates that have been revoked.
* Pull model-CRL is downloaded by the user or organization.
* Push model-CRL is automatically sent out by the CA at regular intervals.
**Online Certificate Status Protocol (OCSP)**- Process designed to query the status of certificate in real-time.
* OCSP stapling is a time-stamped (cached) OCSP response.
37
Key Management
Describes the activities involving the handling of cryptographic keys and other related security parameters. (e.g., passwords) during their lifecycle.
* The includes generation, exchange, store, use strength crypto-shedding (destruction) and replacement.
* *A Key management Practices Statement (KMPS)* is a document tht describes in detail the organizational structure, responisble roles and rules for key management.
38
Key Management Best Practices
1). **Usage-** A key should only be used for one purpose (e.g. encryption).
* *The use of the same key for different cryptographic purposes may weaken the security provided by one or both.*
2). **Strength-**The strength of the key should be commensurate with the data/process protection requirements.
* 3)**Storage**-Private keys must be securely stored. The measures taken to protect a private key must be at least equal to the required security of the use of the key.
* *A hardware security module (HSM) can be used to store cryptographic keys in tamper resistant hardware providing both logical and physical protection (plug-in card or external device).*
39
Key Escrow
Is a proactive arrangement in which keys needed to decrypt data are held in escrow so that, under certain circumstances, an authorized third party may gain access to those keys.
40
What type of certificate does a CA have?
A CA has a root certificate, which it uses to sign certificates.
41
If you are going to use a CA internally what type of CA should you choose?
You would use a private CA for internal use only; these certificates will not be accepted outside of your organization.
42
If you want to carry out B2B activity with third-party companies or sell products on the web, waht type of CA should you use?
| B2B=Business to Business
You would use a public CA for B2B.
43
Why should you take your CA offline when not in use?
If you were a military, security, or banking organization, you would keep the CA offline when it is not being used to prevent it from being compromised.
44
What type of encryption does PKI use?
| PKI=Public Key infrastructure
PKI uses asymmetric encryption.
45
Who signs X509 certificates
The CA signs the X509 certificate.
46
What can you use to prevent your CA from being compromised and fradulent certificates from being issued?
Certificate pinning can be used to prevent a CA from being compromised and fraudulent certificates from being issued.
47
If two entiteis want to setup a cross-certification, what must they setup first?
If two separate PKI entities want to setup cross-certificaton, the root CAs would set up a trust model between themselves, known as a bridge trust model.
48
What type of trust model does the PGP use?
| PGP=Pretty Good Privacy
PGP uses a trust model known as a web of trust.
49
How can you tell whether your certificate is valid?
A Certificate Revocation List (CRL) is used to determine whether a certificate is valid.
50
If the CRL is going slowly, what should you implement?
If the CRL is going slow, you should use OCSP as it provides faster validation.
* Use OCSP instead of CRLs: Online Certificate Status Protocol (OCSP) provides real-time revocation status information without the need for downloading and parsing a large CRL. OCSP can be faster and more efficient than CRLs, especially in high-traffic environments.
| OCSP=Online Certificate Status Protocol
51
Explain certificate stapling/OCSP stapling
Certificate stapling/OCSP stapling is where a web server uses and OCSP for faster certificate authentication, bypassing CRL.
52
What is the process of obtaining a new certificate?
You would submit a Certificate Signing Request (CSR) to request a new certificate.
53
What is the purpose of the key escrow?
The key escrow stores and manages private keys for third parties.
54
What is the purpose of the HSM?
| HSM=Hardware Security Module
A hardware security module (HSM) is used by the key escrow to securely store and manage certificates.
55
What is the purpose of the DRA, and what does it need to complete its role effectively?
| DRA=Disaster Recovery Agent
The purpose of the Disaster Recovery Agent (DRA) is to recover data when a user's private key becomes corrupt. To do this, it must first obtain a copy of the private key from the key escrow.
56
How can you identify each certificate?
Each certificate can be identified by its OID, which is similar to a serial number.
| OID=Object identifyer
57
What format (PKCS is a private certificate, and what file extension does it have?
| PKCS =Public-Key Cryptography Standards
A private certificate is in P12 format with a .pfx extension.
58
What format (PKCS) is a public certificate, and what file extension does it have?
| PKCS =Public-Key Cryptography Standards
A public certificate is in P7B format with a .cer extension.
59
What format is a PEM certificate?
A PEM certificate is Base64 format.
60
What type of certificate can be used on multiple servers in the same domain?
A wildcard certificate can be used on multiple servers in the same domain.
61
What type of certificate can be used on multiple domains?
A Subject Alternative Name (SAN) certificate can be used on multiple domains.
62
What should you do with your software to verify that it is original and not a fake copy?
You would code-sign the software in order to verify that it is the original, and not a copy. This is similar to a digital signature in that it ensures the integrity of the software.
63
What is the purpose of extended validation of an X509?
Extended validation is normally used by financial institutions to provide a higher level of trust for the X509.
64
What type of cipher is the Caesar cipher, and how does it work if it uses ROT 4?
The Caesar cipher is a substituion cipher; an example would be ROT 4, where each letter would be substitued by a letter four characters along in the alphabet.
65
What is encryption, and what are the inputs and outputs called?
Encryption is when plain text (input) is taken and turned into cipher text (output).
66
What type of encryption will be used to encrypt large amounts of data?
Symmetric encryption is used to encrypt large amounts of data as it uses one key.
67
What is the purpose of Diffie-Hellman?
Diffie-Hellman (DH) is an asymmetrice technique that creates a secure tunnel. During a VPN connection, it is used during the IKE phase and uses UDP port 500 to create the VPN tunnel.
| IKE=Internet Key Exchange
68
IKE (Internet Key Exchange)
is a protocol used in IPsec VPNs (Virtual Private Networks) to establish secure communication channels between two endpoints. IKE uses a series of phases to negotiate and establish a secure connection. One of these phases, called IKE Phase 1, uses the Diffie-Hellman key exchange algorithm to establish a shared secret key between the endpoints.
69
What is the first stage in asymmetric encryption?
The first stage in encryption is key exchange. During asymmetric encryption, each entity will give the other entity its public key. The private key is secure and never given away.
70
If Carol is encrypting data to send to Bob, what key will each of them use?
1. Carol uses Bob's public key to encrypt the data.
2. and then Bob will use his private key to decrypt the data.
3. Encryption and decryption are always don by the same key pair.
71
If George encrypted data four years ago with an old CAC card, can he decrypt the data with his new CAC card?
No. George must obtain the old private key to decrypt the data as the encryption as done with a different key pair.
72
If Janet is digitally signing an email to send to John to prove that it has not been tampered with in transit, what key will they each use?
Janet will digitally sign the email with her private key and John will check its validity with Janet's public key; which he should have received in advance.
73
What two things does a digital email signature provide?
A digital signature provides both integrity and non-repudiation.
74
What asymmetric encryption algorithm should you use to encrypt data on a smartphone?
ECC will be uesed to encrypt data on a smartphone as it is small and fast and uses the DH handshake.
| ECC =Elliptic Curve Cryptography
75
What should you use to encrypt a military mobile telephone?
You would use AES-256 to encrypt a military mobile phone.
76
Name two key-stretching algorithms.
Two key stretching algorithms are bcrypt and PBKDF2.
77
Explain how key stretching works.
Key stretching salts the password being stored to prevent duplicate passwords. It also increases the length of the keys to make things harder for a brute-force attack.
78
What is the difference between stream and block cipher modes, and which one will you use to encrypt large blocks of data?
Stream ciphers encrypt one bit at a time and block ciphers take blocks of data, such as 128-bit modes. you would use a block cipher for large amounts of data.
79
What happens with cipher block chaining if you don't have all of the blocks?
CBC needs all of the blocks of data to decrypt the data; otherwise it will not work.
| CBC=Cipher Block Chain
80
If you want to ensure the integrity of data, what should you use? Name
two algorithms.
Hashing ensures the integrity of data; two examples include SHA-1 (160-bit) and MD5 (128-bit)
81
If you want to ensure the protection of data, what should you use?
Encryption is used to protect data so that it cannot be reviewed or accessed.
82
Is a hash a one-way or two-way function, and is it reversible?
A hash is one-way and cannot be reversed.
83
What type of man-in-the-middle attack is SSL 3.0 (CBC) vulnerable to?
POODLE is a man-in-the-middle attack on a downgraded SSL 3.0 (CBC)
| POODLE attack (Padding Oracle On Downgraded Legacy Encryption).
84
Define Diffie Hellman Ephemeral (DHE) and Elliptic Curve Diffie Hellman
Ephemeral (ECDHE).
Diffie Hellman Ephemeral (DHE) and Elliptic Curve Diffie Hellman Ephemeral are both ephemeral keys that are short-lived, one-time keys.
85
What are the strongest and weakest methods of encryption with an L2TP/IPSec VPN tunnel?
The strongest encryption for an L2TP/IPSec VPN tunnel is AES, and the weakest is DES.
86
What is the name of the key used to ensure the security of communication between
a computer and a server or a computer to another computer?
A session key ensures the security of communications between a computer and a server or a computer and another computer.
87
What should you do to protect data-at-rest on a laptop?
You would use an FDE to protect data-at-rest on a laptop
| FDE=Full Disk Encryption
88
What should you do to protect data-at-rest on a tablet or smartphone?
You would use an FDE to protect data-at-rest on a tablet or smartphone.
89
What should you do to protect data-at-rest on a backend server?
Data-at-rest on a backend server is stored on a database. therefore, to protect it you would encrypt the database.
90
What should you do to protect data-at-rest on a removable device, such as a USB flash drive or an external hard drive?
You would protect data-at-rest on a USB flash drive or external hard dirve via full disk encryption.
91
What protocols could you use to protect data in-transit?
You can secure data in-transit using TLS, SSL, HTTPS, or an L2TP/IPSec tunnel.
92
How can you protect data-in-use?
You can protect data-in-use with full memory encryption.
93
What is the purpose of obfuscation?
Obfuscation is used to make the source code look obscure so that if it is stolen, it cannot be understood. It masks the data and could use eitehr XOR or ROT13
94
What is the purpose of perfect forward secrecy?
Perfect forward secracy ensures that there is no link between the server's private key and the sesson key. If the VPN server's key was compromised, it could not decrypt the session. It would be great for use on voting machines.
95
What type of attack tries to find two hash values that match?
A collision attackis whee two hash values match.
96
What is the purpose of rainbow tables?
Rainbow tables are a list of precomputed words shoing their hash value used to crack the hash value of passwords. you will get rainbow tables for MD5 and different rainbow tables for SHA-1
97
Explain the concept of steganography.
Steganography is used to conceal data inside another form of data. You can hide a file, image, video or audio inside another image, video, or audio file.
98
What are the two purposes of Data Loss Protection (DLP)?
DLP prevents sensitive or PII information from being emailed out of a company or being stolen from a file server using a USB device.
99
What is the purpose of salting a password?
Salting a password ensures that duplicate passwords are never stored and makes things more difficult for brute-force attacks by the key side (key-stretching). It appends the salt to the password making it longer than before hashing.
100
Temporary key generated for a connection and never used again?
Ephemeral key
101
Technique to strengthen a weak key to protect against brute-force attacks
Keystretching
Two types:
PBKDZF2
bcrypt
102
is a key derivation function used to derive cryptographic keys from passwords or passphrases.
PBKDF2 (Password-Based Key Derivation Function 2)
*The "PBKDF2 with HMAC-SHA-256" (PBKDF2-HMAC-SHA256) is a specific variant of the PBKDF2 algorithm that uses the HMAC-SHA-256 (Hashed Message Authentication Code using Secure Hash Algorithm 256
103
is a password hashing function that is widely used for secure password storage. It was designed to be slow and computationally intensive, making it more difficult for attackers to crack passwords through brute-force attacks or other methods.
bcrypt
*bcrypt uses the Blowfish encryption algorithm to encrypt passwords, and also incorporates a salt value to make each password hash unique. The number of iterations used in the encryption process can also be adjusted, making it possible to increase the computational cost of generating password hashes.
104
Is a symmetric-key block cipher encryption algorithm designed by Bruce Schneier in 1993. It is widely used for a variety of applications, including secure file transfer protocols, password storage, and virtual private network (VPN) technologies.
Blowfish
*Blowfish uses a variable-length key, from 32 bits to 448 bits, and operates on 64-bit blocks of data. It uses a Feistel network structure, which involves splitting the input block into two halves and performing multiple rounds of encryption and permutation on each half.
One of the key advantages of Blowfish is its speed and efficiency.
105
Hashing algorithm that has been shown to be subject to collision attacks and is deprecated.
MD5
Message Digest (MDX)
*MD5 is a one-way hash function that generates a fixed-length 128-bit hash value from an input message.
106
Hashing algorithm created by NSA
Secure Hash Algorithm (SHA)
SHA-1 has been shown to be subject to collision attacks
SHA-2 family is widely used and includes SHA-256, SHA-384, SHA-512, SHA-512/224, and SHA-512/256.
*SHA-2 takes an input message of any length and produces a fixed-length hash value.
*The SHA-2 hash functions are resistant to a wide range of attacks, including collision attacks, preimage attacks, and second-preimage attacks.
*SHA-2 is widely used for a variety of security applications, including digital signatures, password storage, and SSL/TLS encryption. I
107
Hashing algorithm based on MD4
RIPEMD
*has been replaced by RIPE-160
108
Is the operation performed to encrypt (encode) or decrypt (decode) data.
An algorithm used to encrypt or decrypt data.
The process (or algorithm) used to encrypt and decrypt a message.
Cipher
109
The science and practice of altering data to make it unintelligible to unauthorized parties
Cryptography
110
Security through ___ means keeping something a secret by hiding it.
obscurity
111
Unencrypted data that is meant to be encrypted before it is transmitted, or the result of decryption of encrypted data. An unecrypted message.
| AKA cleartext
Plaintext
112
Data that has been enciphered and cannot be read without the cipher key. An encrypted message
Ciphertext
113
The science, art, and practice of breaking codes and ciphers.
The art of cracking cryptographic systems.
Cryptanalysis
114
A function that converts an arbitrary length string input to a fixed length string output. A cryptographic hash function does this in a way that reduces the chance of collisions, where two different inputs produce the same output.
The output can be referred to as a checksum, message digest, or ___
Hashing
| A hashing algorithm is used to prove integrity
115
A cryptographic hashing algorithm created to address possible weaknesses in MDA.
Considered the strongest algorithm. There are variants that produce different-sized outputs, with longer digests considered more secure. The most popular variant is ___-256, which produces a 256-bit digest.
Secure Hash Algorithm (SHA)
116
A cryptographic hash function producing a 128-bit output.
produces a 128-bit digest.
___is not considered to be quite as safe for use as SHA-256, but it might be required for compatibility between security products.
Message Digest Algorithm #5 (MD5)
117
In cryptography, a specific piece of information that is used in conjunction with an algorithm to perform encryption and decryption.
The use of a ___ with the encryption cipher ensures that decryption can only be performed by authorized persons.
Key
118
A cryptographic ___ is a mathematically complex modern cipher
Algorithm
119
Moves characters or bits to another place within the message block.
Transpositon cipher
The units in a tranportation cipher stay the same in plaintext and ciphertext, but their order is changed, according to some mechanism. Consider how the ciphertext "HLOOLELWRD" has been produced:
H L O O L
E L W R D
| diffusion
120
A ___cipher involves replacing units (a letter or blocks of letters) in the plaintext with different ciphertext. Simple ___ ciphers rotate or scramble letters of the alphabet. For example, ROT13 (an example of a Caesar cipher) rotates each letter 13 places (so A becomes N for instance). The ciphertext "Uryyb Jbeyq" means "Hello World".
substitution cipher
For example, ROT13 (an example of a Caesar cipher) rotates each letter 13 places (so A becomes N for instance). The ciphertext "Uryyb Jbeyq" means "Hello World".
| confusion
121
A ___ cipher is one in which encryption and decryption are both performed by the same secret key. The secret key is so-called because it must be kept secret. If the key is lost or stolen, the security is breached.
symmetric cipher
122
A two-way encryption scheme in which encryption and decryption are both performed by the same key. Also known as shared-key encryption.
Symmetric encryption
Symmetric encryption is very fast. It is used for bulk encryption of large amounts of data. The main problem is secure distribution and storage of the key, or the exact means by which Alice and Bob "meet" to agree the key. If Mallory intercepts the key and obtains the ciphertext, the security is broken.
Note that symmetric encryption **CANNOT ** be used for **AUTHENTICATION** or **INTEGRITY**, because Alice and Bob are able to create exactly the same secrets, because they both know the same key.
!!!!NOTE!!!!Symmetric encryption is also referred to as single key or private key or shared secret.
!!!!Note!!!! that "private key" is also used to refer to part of the public key cryptography process, so take care not to confuse the two uses.
| is used for CONFIDIENTIALITY
123
Two types of symmetric encryption
Stream ciphers and Block ciphers.
124
A type of symmetric encryption that combines a stream of plaintext bits or bytes with a pseudorandom stream initialized by a secret key.
Each byte or bit of data in the plaintext is encrypted one at a time. This is suitable for encrypting communications where the total length of the message is not known. The plaintext is combined with a separate randomly generated message, calculated from the key and an initialization vector (IV). The IV ensures the key produces a unique ciphertext from the same plaintext.
Stream cipher
125
A type of symmetric encryption that encrypts data one block at a time, often in 64-bit and 128-bit, but 128-bit is most common. It is usually more secure, but is also slower, than stream ciphers.
The plaintext is divided into equal-size blocks (usually 128-bit). If there is not enough data in the plaintext, it is padded to the correct size using some string defined in the algorithm. For example, a 1200-bit plaintext would be padded with an extra 80 bits to fit into 10 x 128-bit blocks. Each block is then subjected to complex transposition and substitution operations, based on the value of the key used.
Block ciphers
126
A symmetric 128-, 192-, or 256-bit block cipher based on the Rijndael algorithm developed by Belgian cryptographers Joan Daemen and Vincent Rijmen and adopted by the U.S. government as its encryption standard to replace DES.
Is the default symmetric encryption cipher for most products. Basic AES has a key size of 128 bits, but the most widely used variant is AES256, with a 256-bit key.
Advanced Encryption Standard (AES)
127
Is the range of key values available to use with a particular cipher.
The keyspace is roughly equivalent to two to the power of the size of the key. Using a longer key (256 bits rather than 128 bits, for instance) makes the encryption scheme stronger. You should realize that key lengths are not equivalent when comparing different algorithms, however. Recommendations on minimum key length for any given algorithm are made by identifying whether the algorithm is vulnerable to cryptanalysis techniques and by the length of time it would take to "brute force" the key, given current processing resources.
Keyspace
i.e. 56-bits =2^56
256-bits= 2^256
512-bits=2^512
128
an ___cipher, operations are performed by two different but related public and private keys in a key pair.
Each key is capable of reversing the operation of its pair. For example, if the public key is used to encrypt a message, only the paired private key can decrypt the ciphertext produced. The public key cannot be used to decrypt the ciphertext, even though it was used to encrypt it.
Asymmetric ciper
asymmetric encryption is mostly used for authentication and non-repudiation and for key agreement and exchange.
| can be used to prove identity
129
Widely implemented.
Defacto commercial standard.
Works with both encryption and digital signatures.
Named for its designers, Ronald Rivest, Adi Shamir, and Len Adelman, the first successful algorithm for public key encryption with a variable key length and block size. Published in 1977.
RSA algorithm
| Asymmetric algorithm
130
An asymmetric encryption algorithm that leverages the algebraic structures of elliptic curves over finite fields to derive public/private key pairs.
Similar function to RSA but with smaller key sizes (requires less computing power).
Current US Government standard.
Eliptic Curve Cryptosystem (ECC)
***well-suited for use in environments with limited computational resources, such as mobile devices and IoT devices.
| Asymmetric algorithm,
131
Mathematical ciphers that use an operation which is simple to perform one way when all of the values are known, but is difficult to reverse.
Trapdoor function
132
A message digest encrypted using the sender's private key that is appended to a message to authenticate the sender and prove message integrity.
A __ is a message digest that has been encrypted using the senders private key.
The goal of a ___ is integrity and non-repudiation.
Digital Signature
133
___is the assurance that the data has not been modified
Integrity
134
___means the signer cannot deny sending the message. Conversly the receiver can trust that the message came from the named signer
Non-repudiation.
135
public key encryption standard used for digital signatures that provides authentication and integrity verification for messages.
Published by NIST in cooperation with the NSA.
US government standard
Digital Signature Algorithm (DSA)
*uses elliptic curve cryptography (ECC) rather than the RSA cipher.
136
Any method by which cryptographic keys are transferred among users, thus enabling the use of a cryptographic algorithm.
Key exchange
137
A characteristic of transport encryption that ensures if a key is compromised the compromise will only affect a single session and not facilitate recovery of plaintext data from other sessions.
Perfect forward secrecy (PFS)
| uses Diffie-Hellman to create ephemeral session keys
138
Primarily used for key agreement (key exchange)
Allows two parties (in same DH group) that have no prior knowlege of each other to jointly establish a shared secret key
Diffie-Hellman (DH)
| Asymmetric Algorithm
139
In cryptography, a key that is used within the context of a single session only.
Temporary key generated for a connection and never used again.
Ephemeral
140
PFS can be implemented using either __ or __ algorithms
The Diffie-Hellman Ephemeral mode (DHE or EDH)
or
Elliptic Curve Diffie-Hellman Ephemeral mode (ECDHE)
141
In 2014, a ___was discovered in the way some versions of OpenSSL work that allows remote users to grab 64K chunks of server memory contents (heartbleed.com). This could include the private key, meaning that any communications with the server could be compromised. The bug had been present for around two years. This illustrates the value of PFS, but ironically many servers would have been updated to the buggy version of OpenSSL to enable support for PFS.
Heartbleed bug
142
Implementation of a block symmetric cipher, with some modes allowing secure encryption of a stream of data, with or without authentication for each block.
Mode of operation
143
An encryption mode of operation where an exclusive or (XOR) is applied to the first plaintext block
Cipher Block Chaining (CBC)
| XOR is a logical operation that outputs 1 only when the inputs are 1 & 0
144
An encryption mode of operation where a numerical counter value is used to create a constantly changing IV. Also referred to as CTM (counter mode) and CM (counter mode).
Counter Mode (CTM)
145
Proving the integrity and authenticity of a message by combining its hash with a shared secret.
Message Authentication Code (MAC)
