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1. Top results related to symmetric cryptography

   • Symmetric Encryption Cryptography in Java

     Cryptography is the study of different techniques to secure data from an unauthorized entity. In computer science, we try to develop strategies and practices for protecting sensitive data. Most of the cryptography involves very advanced Mathematical functions used for securing data. The sole purpose of the algorithms developed for cryptography is to hide data from the attacker or middleman. In this article, we will understand the concept in cryptography named symmetric encryption.  Before getting into the concept, lets first understand a few key terms involved in cryptography. They are:  

     • Plain text: The plain text is the original message or data that is hidden from view through a cryptographic encryption algorithm.
     • Cipher text: It is the output of Encryption operation when given key and plain text. It is also the data fed to a Decryption function.

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   • Initialization vector - best practices (symmetric cryptography)

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     Answered Feb 03, 2019 · 7 votes

     IV selection is a bit complicated because the exact requirements depend on the mode of operation. There are some general rules, however:

     • You can't go wrong¹ with a random IV, except when using shorter IVs in modes that allow this.
     • Never use the same IV with the same key.
     • If you only ever encrypt a single message with a given key, the choice of IV doesn't matter².
     • Choose the IV independently of the data to encrypt.
     • Never use ECB.

     Of the most common specific modes of operation:

     • CBC requires the IV to be generated uniformly at random. Do not use a counter as IV for CBC. Furthermore, if you're encrypting some data that contains parts that you receive from a third party, don't reveal the IV until you've fully received the data, .
     • CTR uses the IV as the initial value of a counter which is incremented for every block, not for every message, and the counter value needs to be unique for every block. A block is 16 bytes for all modern symmetric ciphers (including AES, regardless of the key size). So for CTR, if you encrypt a 3-block message (33 to 48 bytes) with 0 as the IV, the next message must start with IV=3 (or larger), not IV=1.
     • Modern modes such as Chacha20, GCM, CCM, SIV, etc. use a nonce as their IV. When a mode is described as using a nonce rather than an IV, this means that the only requirement is that the IV is never reused with the same key. It doesn't have to be random.

     When encrypting data in a database, it is in general not safe to use the row ID (or a value derived from it) as IV. Using the row ID is safe only if the row is never updated or removed, because otherwise the second time data is stored using the same ID, it would repeat the IV. An adversary who sees two different messages encrypted with the same key and IV may well be able to decrypt both messages (the details depend on the mode and on how much the attacker can guess about the message content; note that even weak guesses such as “it's printable UTF-8” may suffice).

     Unless you have a very good reason to do otherwise (just saving a few bytes per row does not count as a very good reason) and a cryptographer has reviewed the specific way in which you are storing and retrieving the data:

     • Use an authenticated encryption mode such as GCM, CCM, SIV or Chacha20+Poly1305.

     The reason to increment the counter first is that if the process is interrupted, it will lead to a skipped counter value, which is not a problem. If step 2 was done without step 1, it would lead to repeating a nonce, which is bad. With this scheme, you can shave a few bytes off the nonce length if the mode allows it, as long as the length is large enough for the number of messages that you'll ever encrypt.

     If you don't have such a counter, then use the maximum nonce length and generate a random counter. The reason to use the maximum nonce length is that due to the birthday paradox, a random n-bit nonce is expected to repeat when the number of messages approaches 2n/2.

     In either case, you need to store the nonce in the row.

     • If you can store a counter somewhere and make sure that it's never reset as long as you keep using the same encryption key, then each time you encrypt a message: Increment the counter.Use the new value of the counter as the nonce for the authenticated encryption.The reason to increment the counter first is that if the process is interrupted, it will lead to a skipped counter value, which is not a problem. If step 2 was done without step 1, it would lead to repeating a nonce, which is bad. With this scheme, you can shave a few bytes off the nonce length if the mode allows it, as long as the length is large enough for the number of messages that you'll ever encrypt.
     • If you don't have such a counter, then use the maximum nonce length and generate a random counter. The reason to use the maximum nonce length is that due to the birthday paradox, a random n-bit nonce is expected to repeat when the number of messages approaches 2n/2.
     • In either case, you need to store the nonce in the row.

     ¹ Assuming that everything is implemented correctly, e.g. random values need to be generated with a random generator that is appropriate for cryptography. ² As long as it isn't chosen in a way that depends on the key.

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   • Can symmetric cryptography be used for providing digital signatures?

     Top Answer

     Answered Jun 02, 2017 · 2 votes

     With a symmetric key, anyone who could check the signature could also forge a signature. For most of the use cases of digital signatures, we want untrusted parties to be able to verify the signature. That requires that the key you use to check that a signature is correct be insufficient to generate a valid signature, and that requires asymmetric cryptography by definition.

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   • cryptography.fernet.InvalidToken problem with cryptography

     Top Answer

     Answered Oct 26, 2022 · 1 votes

     I have found out, through trial and error with the same project later down the line, that you need to turn your key into something like this key = b'niwaXsYbDiAxmLiqRiFbDa_8gHio15sNQ6ZO-sQ0nR4='

     The main difference being the key is encoded in a utf-8 format and is now readable by Fernet and doesn't return that error. Here is a function that uses Tkinter, Fernet, and os to actually decrypt my file.

     # Propriatary method of encrypting filesdef decrypt(self, file): with open(file, 'rb') as readfile: contents = readfile.read()- self.title(os.path.basename(file) + ' - SecureNote') # self.textbox is a variable inside of the class I am using for my window self.textbox.delete(1.0, tk.END)- if contents != "": # getword retur Key = bytes(getword('Key:', 1), encoding="utf-8") fernet = Fernet(Key)- decrypted = fernet.decrypt(contents).decode('utf-8') self.textbox.insert(1.0, str(decrypted))- del Key del fernet else: pass-

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2. www.khanacademy.org › computing › computers-andSymmetric encryption (article) | Khan Academy

   www.khanacademy.org › computing › computers-and

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   Learn about symmetric encryption, where the same key is used to encrypt and decrypt data. Explore examples of Caesar Cipher, Vigenère Cipher, and AES-128, and how they work and can be cracked.

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     Symmetric Key Cryptography | Stream Cipher & Block Cipher Explained | Network Security | Simplilearn

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     Lec-81: Symmetric Key Cryptography in Network Security with examples

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     What is Symmetric Encryption? Simply Explained | Venafi Chalk Talk

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4. en.wikipedia.org › wiki › Symmetric-key_algorithmSymmetric-key algorithm - Wikipedia

   en.wikipedia.org › wiki › Symmetric-key_algorithm

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   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]

5. www.geeksforgeeks.org › symmetric-key-cryptographySymmetric Key Cryptography - GeeksforGeeks

   www.geeksforgeeks.org › symmetric-key-cryptography

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   May 2, 2024 · Last Updated : 02 May, 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. This type of cryptography plays a crucial role ...

6. www.techtarget.com › searchsecurity › featureCryptography basics: Symmetric key encryption algorithms

   www.techtarget.com › searchsecurity › feature

   Jan 28, 2020 · Approved for use since the 1970s, symmetric key encryption algorithms are just one way to keep confidential data secure. Take a look at the different algorithms, from DES to AES and their spinoffs, and learn the math behind the crucial cryptography functionality.

   • Author: Sharon Shea

   • Video Duration: 2 min

7. geekflare.com › symmetric-encryptionSymmetric Encryption Explained in 5 Minutes or Less

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   Jun 25, 2023 · Learn what symmetric encryption is, how it works, and why it is important for data security. Compare different symmetric encryption algorithms such as DES, 3DES, and AES, and their advantages and disadvantages.

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8. www.sciencedirect.com › symmetric-cryptographySymmetric Cryptography - an overview | ScienceDirect Topics

   www.sciencedirect.com › symmetric-cryptography

   Learn about symmetric cryptography, also known as secret key cryptography, and its applications, threats, and algorithms. Compare DES, 3DES, AES, and RC2 with examples and code snippets.

9. www.freecodecamp.org › news › encryption-explainedSymmetric and Asymmetric Key Encryption – Explained in Plain ...

   www.freecodecamp.org › news › encryption-explained

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   Apr 5, 2023 · Learn the basics of encryption, algorithms, and keys with examples and analogies. Understand how symmetric and asymmetric key encryption are used for data at rest and in transit, and how TLS/SSL combines them.