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What is symmetric key cryptography?
Why are ciphers called symmetric?
What is asymmetric cryptography?
How does symmetric cryptography work?
May 2, 2024 · Symmetrical Key Cryptography also known as conventional or single-key encryption was the primary method of encryption before the introduction of public key cryptography in the 1970s. In symmetric-key algorithms, the same keys are used for data encryption and decryption.
- Overview
- Vigenère Cipher
- Modern ciphers
A symmetric encryption is any technique where the same key is used to both encrypt and decrypt the data. The Caesar Cipher is one of the simplest symmetric encryption techniques, and of course, one of the easiest to crack.
Since then, cryptologists have invented many more symmetric encryption techniques, including the ones used today to encrypt data like passwords.
Encryption
The Vigenère cipher uses an entire word as the shift key, as opposed to the Caesar Cipher’s single shift amount. Imagine that we want to encrypt the phrase VERSAILLES and use a shift key of CHEESE. First, we need to repeat the shift key to line up with each of the letters in the phrase: Now we replace each letter of the original text according to the Vigenère table: For the first letter "V", we select the row that starts with "V". Then since the corresponding shift key letter is "C", we move to the column that has a header of "C". The letter at the intersection of the "V" row and "C" column is "X". Thus, we encrypt "V" as "X". The letter at the intersection of the "E" row and "H" column is "L", so we encrypt "E" as "L". If we keep going, we'll end up with the encrypted text "XLVWSMNSIW". your understanding If we want to use a different shift key of "PIZZA" to encrypt "VERSAILLES", what will the first letter "V" be encrypted as? Choose 1 answer: Choose 1 answer: •(Choice A) X •(Choice B) K •(Choice C) P •(Choice D) A •(Choice E) T Check
Decryption
Imagine that we receive the encrypted message "NVYZJI" from our ally, and we know they've used a Vigenère cipher with a shift key of "CHEESE". Once again, we line the encrypted message up with the shift key: Now we can do a reverse substitution according to the table: We start by selecting the row for the first letter in the shift key "C". Then we scan down that row until we find the first encrypted letter "N". Once we find the "N", we look up to see the header for that column, "L". Thus, the decryption of "N" is "L". For the next letter, we select the "H" row, find the "V" in the row, and look up to see we're in column "O". If we do that for each shift key and encrypted letter, we decrypt the entire phrase as "LOUVRE". your understanding If we receive a new message "NVSO" that's encrypted with the same shift key of "CHEESE", what was the original text? Choose 1 answer: Choose 1 answer: •(Choice A) LOVE •(Choice B) LOOK •(Choice C) LONE •(Choice D) LOSE •(Choice E) LOOT Check
Cracking the cipher
The Vigenère Cipher is a type of polyalphabetic cipher, and it's a harder code to crack than the Caesar Cipher due to the use of an entire shift word. If an intercepter had no idea what the shift key was and wanted to brute force their way to a decryption, they would need to try out all the possible shift words in the world, and perhaps even made-up words! For a mere mortal, that could take a lifetime. That's much more work than brute forcing the Caesar Cipher, where we just had to check 26 different shift amounts. What about frequency analysis? Do messages encrypted with the Vigenere cipher have a special pattern in their distribution of letters? Try it out for yourself! Encrypt the message below, and you'll see a frequency analysis of the original message and the encrypted message. Notice that the frequency analysis of the original message is exactly what we'd expect for an English-language message: "E" is the most popular letter, and there is huge variance in the frequency of the letters. The frequencies of the encrypted message are more similar to each other. We can't identify an obvious "E", since the letter "E" gets encrypted into different letters at different points in the message. In the 1800s, people finally figured out different ways to use frequency analysis to crack the cipher. For example, in a long message, a short word like "THE" may get translated to the same three encrypted letters multiple times (just not every time), and that reveals possible lengths for the shift key. Now that we have the use of powerful computers, the Vigenère Cipher is relatively easy to decipher, because a computer can quickly test out millions of words, and it can easily find the leaked information in the frequency analysis.
In the age of computers, ciphers can't just be hard to crack by an enterprising human; they have to be hard to crack by a computer that can do trillions of calculations per second.
Fortunately, cryptologists have invented encryption techniques that are secure in the digital world, and are continuing to improve them every year.
One of the most common encryption standards is AES-128, a block cipher approved by the federal government and used often for secure file transfer.
What makes it so secure?
One reason is that each key is always 128 bits long. That means there are 2128 possible keys. That's this many:
340,000,000,000,000,000,000,000,000,000,000,000,000
Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext. The keys may be identical, or there may be a simple transformation to go between the two keys. [1]
Jun 25, 2023 · Symmetric encryption is a fast and secure type of encryption that uses a single key for encryption and decryption. Encryption is the process of converting human-readable information into a scrambled, unreadable format called ciphertext. This is done to prevent access to sensitive information by unauthorized people.
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Symmetric cryptography, known also as secret key cryptography, is the use of a single shared secret to share encrypted data between parties. Ciphers in this category are called symmetric because you use the same key to encrypt and to decrypt the data.
Aug 7, 2023 · Symmetric Key Cryptography, also known as Symmetric Encryption, is like a secret handshake between two people—it's a shared secret that only they know. In this case, that secret is a key: a piece of information that both the sender and receiver use to lock (encrypt) and unlock (decrypt) messages.
May 19, 2022 · Symmetric encryption, also known as symmetric cryptography or secret key encryption, is a cryptographic protocol where two or more users share a single secret key to encrypt and decrypt communications.
