# A Key That Is Generated By A Symmetric Cryptographic Algorithm

In cryptography, a **key** is a piece of information (a parameter) that determines the functional output of a cryptographic algorithm. For encryption algorithms, a key specifies the transformation of plaintext into ciphertext, and vice versa for decryption algorithms. Keys also specify transformations in other cryptographic algorithms, such as digital signature schemes and message authentication codes.^{[1]}

- A Key That Is Generated By A Symmetric Cryptographic Algorithm Is Said To Be A
- A Key That Is Generated By A Symmetric Cryptographic Algorithm Is Said To Be A
- A Key That Is Generated By A Symmetric Cryptographic Algorithm Is Said To Be A:
- A Key That Is Generated By A Symmetric Cryptographic Algorithm Is Said To Be A

In an asymmetric cryptographic process one key is used to encipher the data, and a different but corresponding key is used to decipher the data. A system that uses this type of process is known as a public key system. The key that is used to encipher the data is widely known, but the corresponding key for deciphering the data is a secret. Oct 18, 2016 The encryption keys generated in modern cryptographic algorithms are generated depending upon the algorithm used. Primarily there are two types of encryption schemes: Symmetric and Asymmetric(Public Key encryption). How many keys are required for secure communication among 1000 person if: Symmetric key encryption algorithm is used? Asymmetric key encryption algorithm is used? My guess: For symmetric they each need to maintain and transfer their own key, so probably $1000 times 1000$, and for asymmetric maybe just $2000$, each having one public one private.

## Need for secrecy[edit]

Symmetric key. In this type of cryptography both the parties (sender and receiver) use same key to encrypt and decrypt the message. A popular symmetric key algorithm is Data Encryption Standard (DES), there are also its modern variants such as Triple DES. Asymmetric key. In this type, there are two keys, public and private. Cryptographic algorithm and key length IBM Security Key Lifecycle Manager uses two types of algorithms, such as symmetric algorithms and asymmetric algorithms for data encryption. Symmetric, or secret key encryption, uses a single key for both encryption and decryption. Symmetric key encryption is used to encrypt large amounts of data efficiently. Fernet (symmetric encryption)¶ Fernet guarantees that a message encrypted using it cannot be manipulated or read without the key. Fernet is an implementation of symmetric (also known as “secret key”) authenticated cryptography. Fernet also has support for implementing key rotation via MultiFernet. Class cryptography.fernet.Fernet (key) source ¶.

In designing security systems, it is wise to assume that the details of the cryptographic algorithm are already available to the attacker. This is known as Kerckhoffs' principle — '*only secrecy of the key provides security*', or, reformulated as Shannon's maxim, '*the enemy knows the system*'. The history of cryptography provides evidence that it can be difficult to keep the details of a widely used algorithm secret (see security through obscurity). A key is often easier to protect (it's typically a small piece of information) than an encryption algorithm, and easier to change if compromised. Thus, the security of an encryption system in most cases relies on some key being kept secret.^{[2]}

Symmetric data key — A symmetric encryption key that you can use to encrypt data outside of AWS KMS. This key is protected by a symmetric CMK in AWS KMS.

Trying to keep keys secret is one of the most difficult problems in practical cryptography; see key management. An attacker who obtains the key (by, for example, theft, extortion, dumpster diving, assault, torture, or social engineering) can recover the original message from the encrypted data, and issue signatures.

## Key scope[edit]

Keys are generated to be used with a given *suite of algorithms*, called a cryptosystem. Encryption algorithms which use the same key for both encryption and decryption are known as symmetric key algorithms. A newer class of 'public key' cryptographic algorithms was invented in the 1970s. These asymmetric key algorithms use a pair of keys—or *keypair*—a public key and a private one. Public keys are used for encryption or signature verification; private ones decrypt and sign. The design is such that finding out the private key is extremely difficult, even if the corresponding public key is known. As that design involves lengthy computations, a keypair is often used to exchange an on-the-fly symmetric key, which will only be used for the current session. RSA and DSA are two popular public-key cryptosystems; DSA keys can only be used for signing and verifying, not for encryption.

## Ownership and revocation[edit]

### A Key That Is Generated By A Symmetric Cryptographic Algorithm Is Said To Be A

Part of the security brought about by cryptography concerns confidence about who signed a given document, or who replies at the other side of a connection. Assuming that keys are not compromised, that question consists of determining the owner of the relevant public key. To be able to tell a key's owner, public keys are often enriched with attributes such as names, addresses, and similar identifiers. The packed collection of a public key and its attributes can be digitally signed by one or more supporters. In the PKI model, the resulting object is called a certificate and is signed by a certificate authority (CA). In the PGP model, it is still called a 'key', and is signed by various people who personally verified that the attributes match the subject.^{[3]}

In both PKI and PGP models, compromised keys can be revoked. Revocation has the side effect of disrupting the relationship between a key's attributes and the subject, which may still be valid. In order to have a possibility to recover from such disruption, signers often use different keys for everyday tasks: Signing with an *intermediate certificate* (for PKI) or a *subkey* (for PGP) facilitates keeping the principal private key in an offline safe.

Deleting a key on purpose to make the data inaccessible is called crypto-shredding.

## Key sizes[edit]

For the one-time pad system the key must be at least as long as the message. In encryption systems that use a cipher algorithm, messages can be much longer than the key. The key must, however, be long enough so that an attacker cannot try all possible combinations.

A key length of 80 bits is generally considered the minimum for strong security with symmetric encryption algorithms. 128-bit keys are commonly used and considered very strong. See the key size article for a more complete discussion.

The keys used in public key cryptography have some mathematical structure. For example, public keys used in the RSA system are the product of two prime numbers. Thus public key systems require longer key lengths than symmetric systems for an equivalent level of security. 3072 bits is the suggested key length for systems based on factoring and integer discrete logarithms which aim to have security equivalent to a 128 bit symmetric cipher. Elliptic curve cryptography may allow smaller-size keys for equivalent security, but these algorithms have only been known for a relatively short time and current estimates of the difficulty of searching for their keys may not survive. As early as 2004, a message encrypted using a 109-bit key elliptic curve algorithm had been broken by brute force.^{[4]} The current rule of thumb is to use an ECC key twice as long as the symmetric key security level desired. Except for the random one-time pad, the security of these systems has not been proven mathematically as of 2018, so a theoretical breakthrough could make everything one has encrypted an open book (see P versus NP problem). This is another reason to err on the side of choosing longer keys.

## Key choice[edit]

### A Key That Is Generated By A Symmetric Cryptographic Algorithm Is Said To Be A

To prevent a key from being guessed, keys need to be generated truly randomly and contain sufficient entropy. The problem of how to safely generate truly random keys is difficult, and has been addressed in many ways by various cryptographic systems. There is a RFC on generating randomness (RFC 4086, *Randomness Requirements for Security*). Some operating systems include tools for 'collecting' entropy from the timing of unpredictable operations such as disk drive head movements. For the production of small amounts of keying material, ordinary dice provide a good source of high quality randomness.

## Key vs password[edit]

For most computer security purposes and for most users, 'key' is not synonymous with 'password' (or 'passphrase'), although a password can in fact be used as a key. The primary practical difference between keys and passwords is that the latter are intended to be generated, read, remembered, and reproduced by a human user (though the user may delegate those tasks to password management software). A key, by contrast, is intended for use by the software that is implementing the cryptographic algorithm, and so human readability etc. is not required. In fact, most users will, in most cases, be unaware of even the existence of the keys being used on their behalf by the security components of their everyday software applications.

If a password*is* used as an encryption key, then in a well-designed crypto system it would not be used as such on its own. This is because passwords tend to be human-readable and, hence, may not be particularly strong. To compensate, a good crypto system will use the *password-acting-as-key* not to perform the primary encryption task itself, but rather to act as an input to a key derivation function (KDF). That KDF uses the password as a starting point from which it will then generate the actual secure encryption key itself. Various methods such as adding a salt and key stretching may be used in the generation.

## See also[edit]

### A Key That Is Generated By A Symmetric Cryptographic Algorithm Is Said To Be A:

- Cryptographic key types classification according to their usage
- Diceware describes a method of generating fairly easy-to-remember, yet fairly secure, passphrases, using only dice and a pencil.
- glossary of concepts related to keys

## References[edit]

**^**'What is cryptography? - Definition from WhatIs.com'.*SearchSecurity*. Retrieved 2019-07-20.**^**'Quantum Key Generation from ID Quantique'.*ID Quantique*. Retrieved 2019-07-20.**^**Matthew Copeland; Joergen Grahn; David A. Wheeler (1999). Mike Ashley (ed.). 'The GNU Privacy Handbook'.*GnuPG*. Archived from the original on 12 April 2015. Retrieved 14 December 2013.**^**Bidgoli, Hossein (2004).*The Internet Encyclopedia*. John Wiley. p. 567. ISBN0-471-22201-1 – via Google Books.

## Cryptography

Derrick Rountree, in Security for Microsoft Windows System Administrators, 2011

### Asymmetric Encryption

Asymmetric encryption is also referred to as public key encryption. In asymmetric encryption, both the encrypting and decrypting systems have a set of keys. One is called the public key, and another is called the private key. If the message is encrypted with one key in the pair, the message can be decrypted only with the other key in the pair.

Asymmetric key algorithms are not quite as fast as symmetric key algorithms. This is partially due to the fact that asymmetric key algorithms are generally more complex, using a more sophisticated set of functions.

#### Asymmetric Key Algorithms

Asymmetric key algorithms aren't as widely used as their symmetric counterparts. So we'll just go over two of the big ones: Diffie-Hellman and RSA.

*Diffie-Hellman*: The Diffie-Hellman algorithm was one of the earliest known asymmetric key implementations. The Diffie-Hellman algorithm is mostly used for key exchange. Although symmetric key algorithms are fast and secure, key exchange is always a problem. You have to figure out a way to get the private key to all systems. The Diffie-Hellman algorithm helps with this. The Diffie-Hellman algorithm will be used to establish a secure communication channel. This channel is used by the systems to exchange a private key. This private key is then used to do symmetric encryption between the two systems.

*RSA*: It is the Rivest Shamir Adelman algorithm. RSA was developed in 1978. RSA was the first widely used asymmetric algorithms used for signing and encryption. It supports key lengths of 768 and 1,024 bits. The RSA algorithm uses a three-part process. The first part is key generation. The keys used in the RSA algorithm are generated using mathematical operations based on prime numbers. The second part of the process is encryption. This encryption is done using one of the keys in the key pair. The third part of the process is decryption. The decryption is done using the other key in the key pair.

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