Asymmetric algorithm . It is an algorithm that modifies the data of a document in order to achieve some security features such as authentication, integrity and confidentiality. Also known as public key algorithms.
Summary
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- 1 Definition
- 2 Specifications
- 3 Security
- 4 Advantages and disadvantages
- 5 algorithms
- 6 See also
- 7 Sources
Definition
Its main feature is that it is not based on a single key but on a couple of them: a known Public and a Private one. Currently there are many algorithms of this type but they have proven to be of little use in practice, either due to the length of the keys, the length of the generated encrypted text or their extremely long encryption speed.
specs
In asymmetric algorithms, a key pair is used to send messages. The two keys belong to the same person who sent the message. One key is public and can be given to anyone, the other key is private and must be kept by the owner so that no one has access to it. Furthermore, cryptographic methods ensure that this key pair can only be generated once, so it can be assumed that it is not possible for two people to have casually obtained the same key pair.
If the sender uses the recipient’s public key to encrypt the message, once encrypted, only the recipient’s private key will be able to decrypt this message, since it is the only one that knows it. Therefore the confidentiality of the sending of the message is achieved, nobody except the recipient can decipher it.
If the owner of the key pair uses their private key to encrypt the message, anyone can decrypt it using their public key. In this case, the identification and authentication of the sender is therefore achieved, since it is known that only he could have used his private key. This idea is the foundation of the electronic signature. Public key encryption systems or asymmetric encryption systems were invented in order to completely avoid the key exchange problem of symmetric encryption systems. With public keys, it is not necessary for the sender and the recipient to agree on the key to use.
All that is required is that, before initiating the secret communication, the sender obtain a copy of the recipient’s public key. What’s more, that same public key can be used by anyone who wants to communicate with its owner. Therefore, only n key pairs will be needed for every n people who want to communicate with each other.
Security
According to the second Kerckhoffs principle, all security should not fall on the algorithm, rather on the key. Therefore, the key size is a measure of system security, but the size of the symmetric encryption key cannot be compared to that of the public key encryption to measure security. In a brute force attack on symmetric encryption with a key the size of 80 bits, the attacker must test up to 280-1 keys to find the correct key.
In a brute force attack on a public key encryption with a key the size of 512 bits, the attacker must factor a composite number encoded in 512 bits. The amount of work for the attacker will be different depending on the encryption that is attacking. While 128 bits is sufficient for symmetric encryption, given today’s factoring technology, the use of 1024-bit public keys is recommended for most cases.
Advantages and disadvantages
The biggest advantage of asymmetric cryptography is that the key distribution is easier and more secure since the key that is distributed is the public one, keeping it private for the exclusive use of the owner, but this system has quite a few disadvantages: For a same key length and message takes longer processing time. Keys must be larger than symmetric keys.
The encrypted message takes up more space than the original. The new asymmetric key systems based on elliptic curves have less expensive features. Tools such as PGP , SSH or the SSL security layer for the TCP / IP protocol hierarchy use a hybrid consisting of asymmetric cryptography to exchange symmetric cryptographic keys, and symmetric cryptography for the transmission of information.
Algorithms
Of the algorithms that use public key or are asymmetric as they are also known among them are:
- Diffie-Hellman
- RSA
- DSA
- ElGamal
- Merkle-Hellman
- Knapsack
