1.4 Protection of bits, 1.5 Hashing

• ⭐️ one exercise of ECC on paper
• ⭐️ one exercise on CRC, how to use polynomial, and how to get checksum
• ⭐️ how CRC works
• ⭐️ what is hashing
• ⭐️ what is salt, pepper
• ⭐️ what is firewall
• ⭐️ what is DMZ
• ⭐️ what is mirroring
• ⭐️ three types of clouding, what is the idea of contracting a compnay for…
• ⭐️ 5’ 9s availability: How do you give to company that has…
• ⭐️ UPS: what is the name of energy not stopped…
• ⭐️ DPC: how do you call these centers that…

☑️ ECC and CRC

• 🛠️ protection for transport/download
• network
• protection for files

✅ ECC

Error Checking and Correction
added by groups

• add extra bits(Redundance) in order to correct possible failures
• send extra information to check if the information is correct
• need to transmit both data + extra bits
• several ECC techniques exists, each technique has its own subset creating method

✔️ How to apply ECC

• 1️⃣ Initial sequence
• 2️⃣ Create subsets of bits of the initial sequence
  • each ECC technique has its own subset creating method
• 3️⃣ On each subset, apply an even parity
• 4️⃣ All extra 1s are added at the end of the sequence
• 5️⃣ Using the extra 1s we can use reverse engineering to find the original initial sequence
• 👉🏻 We can check if the initial sequence has been changed using the extra 1 bits

📌 Even parity

• 👉🏻 even parity: number of 1s has to be even

• if number of 1 is even, add 0
• if number of 1 is odd, add an extra 1

✔️ Example of subsets

• subset 1: 0100
• ➡️ odd number of 1s
• ➡️ according to even parity, need to add extra 1 to make it even
• subset 2: 1101
• ➡️ odd number of 1s
• ➡️ according to even parity, need to add extra 1 to make it even
• subset 3: 0100
• ➡️ odd number of 1s
• ➡️ according to even parity, need to add extra 1 to make it even
• In total, we have to add extra 1, 1, 1 in the end

✔️ Example of getting extra bits

001101011010
( 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, count from right to left, but write from left to write)
subset1 = 1, 2, 3, 4      = 1010 ➡️ do not add ➡️ 0
subset2 = 4, 5, 6, 7      = 1011 ➡️ add extra ➡️ 1
subset3 = 4, 6, 7, 8      = 0101 ➡️ do not add ➡️ 0
subset4 = 9, 10, 11, 12   = 0011 ➡️ do not add ➡️ 0

extra bits: 0100
result: 001101011010 + 0100

❓ What do we need to create a computer with ECC?

• 1️⃣ need a counter to count the extra bits
• 2️⃣ comparison chip to compare if the count of 1s are even or not
• 3️⃣ flag to give you an extra bit if the count of 1 is odd
• normally called ECC flag

📌 Logic Gates

• pre-built chips that perform mathametical operations

✔️ 3 main logic gates

• 1️⃣ chip AND gate
• two for input, one output

• output 1, only if input is both 1 and 1

• 2️⃣ chip OR gate
• two for input, one output

• output 1, whenever there is any 1

• 3️⃣ chip XOR or Exclusive OR
• very picky!
• symbol: OR triangle with a border to the left
• two for input, one output
• output 1, when there is only one 1
• output 1, when there is one 1, but when there is 2 1s, it outputs 0
• 두꺼비집, when electicity is too high, everything goes down
• so when there is too many 1, outputs 0. very picky!

✅ CRC

Cyclic Redundance Code

• send extra bits protected with another extra bit
• however, need to send more data
• more cyles(more redundance) ⬆️ more secure ⬆️ efficiency ⬇️
• uses XOR

✔️ How does CRC work

• CRC = Initial sequence + Polynomial

• each CRC uses has own Polynomial sequence method

• 1️⃣ Convert Polynomial into a sequence of bits
• exponents of the x indicate which bits are 1
• if exponent of Polynomial is 8, 2, 1, 0 then bit position 8, 2, 1, 0 will be 1
• other bits will be 0
• ⭐️ In CRC, has different changes the numbering of the bit
• most right bit is 0
• result: 100000111
• Thus the size of the sequence will depend on the exponent of the Polynomial
• 2️⃣ Write the Polynomial sequence below the original sequence
• starting by the left
• ⭐️ but, discard all the 0s on the left
• 3️⃣ XOR bit by bit
• 4️⃣ the rest of the original sequence, just retype again, copy
• 5️⃣ Now repeat the step 2️⃣~4️⃣, cyclic
• ⭐️ remember, first 0s will be discarded
• 6️⃣ repeat until the final result is shorter or same length as the original polynomial, stops
• 7️⃣ Final result checksum get we get will be added at the end of the original message
• Then, will be transmitted
• 8️⃣ Reciever will perform the reverse engineering, then will check if the message has any errors

✔️ Checksum

• final result of the CRC process
• used to check if the message has arrived correctly

✅ Hashing

• 🛠️ used for protecting passwords
• needs to be more secure than file protection

• example of hashing: yescrypt

• there is always a mathematical function in Hashing ➡️ Hash function
• apply the hash function to the password that you type
• Hashing applies hash function to each of the the original bits
• if my password is ZORRO, as each CHAR is 8 bits, will be 40 bits

• apply hash function to each of the 40 bits

• method for Hashing

✔️ Goal of hashing

• goal is to get something very different from the original password

• even if two passwords are very simmilar, the result will be totally different

• If the system has hashing, you can use simmilar passwords, as they will be converted into totally different results(GMAIL)
• However, if the system does not have hashing, you can not use simmilar passwords(HOTMAIL)

Q: If the teacher can use `hola` and when it expires uses `hola1`, what kind of technology is the systems using?
A: Hashing

✅ Salt

use hashing, use math
store in hard drive

• add salt to a password
• salt: random 0s and 1s, transforming the password before hashing the password
• add salt: get random sequence of 0s and 1s to the original password
• then XOR the salt and the original password
• then hash the result of original password + salt XOR

✔️ Where do we use salt? Where is it stored?

• salt needs to be recorded/stored in order to log in the system
• ⭐️ thus, salt should be stored in the hard-disk of the computer, so it is kept involatile
• which means you can use only that computer for logging in
• we use salt for computers that should be protected themselves

✅ Pepper

use hashing, use math
store in cloud

• store salt(pepper) in a cloud/server
• 1️⃣ Now salt(pepper) can be accessed from all, several computers
• We can log-in from any computer
• not me, but a compnay server would be protecting my salt(pepper)
• 2️⃣ As salt(pepper) is protected by a company, pepper is considered more protected than salt

✔️ Clouds

• clouds are comuters protected physically and logically with protocols

✅ Security

☑️ Logic Security

• Security using software
• example:
• ✔️ Hashing: salt, pepper
• ✔️ Anitivirus

• ✔️ Firewall: machine with specific software that opens or closes ports

  • if I close HTTP, you cannot browse internet
  • if I close SMTP, you cannot send emails

• ✔️ DMZ: Demilitarized Zone, in a company a set of computers that are free of public access with no much protection, normally contain non-essential information

  • having DMZ protects MZ from being extra abused
  • for example, DMZ: public webpage for FP, MZ: my private aula virtual, need to log-in

• ✔️ Mirroring: having my computer mirror/copy another computer

  • mirroring is NOT a backup
  • 👎🏻 backups are not totally updated
  • 👍🏻 mirroring is duplicated in real-time
  • with mirroring, you can sync both computers only when an important and correct
  • can sync just incase you have to go back to the past

• ✔️ Backups: every x months make a backup of your data

  • backups should be taken into isolated environments
• ✔️ Security Patch: software that solves an error found without needing to reinstall the operating system

☑️ Physic Security

• Security using hardware

• ✔️ Clouding: Taking my company data to the cloud

  • Three types of clouding
  • 1️⃣ IaaS: Infrastructure as a Service
    • I do not have computers in my company, I use the computer of another company
    • use the computer of another company, I do not have the infrastructure
    • not very commonly used
  • 2️⃣ Paas: Platform as a Service
    • contract another company’s computers and their software
    • you log-in to their applications
    • a lot of loss of control of your company
    • the platform will not be tailored to your needs
  • 3️⃣ SaaS: Software as a Service
    • Everything belongs to the other company
    • including the products that are created by you
    • very expensive
    • streaming platform, you do not have any rights to keep the movie, paying for the service
    • When a traditional company contracts a company to take the company into the Internet

• ✔️ Security and High Availability(5 9’s)

  • 3 9's: The company is available for 99.9%
  • 4 9's: The company is available for 99.99%
    • Linux OS, AMAZON has a 4 9's certificate
  • 5 9's: The company is available for 99.999%
    • out of 100,000 only 1 will fail
  • systems company always aim for the 5 9's

• ✔️ Load Balancing

  • workload is evenly distributed among the computers
  • apply RAID

• ✔️ UPS

  • Uninterrupted Power System
  • system for solving electicity failures
  • generators

• ✔️ DPC

  • Data Process Centers
  • building specialized in databases
  • need very strict architectural security

• ✔️ Access Controls

  • finger prints

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