# What is the Blowfish encryption used for?

## CISO

Thanks to numerous data leaks and fear of being spied on by NSA and their consorts, encryption has repeatedly come into the public eye. The encryption of data has long been part of mankind's inventory. Read everything you should know about the most important terms and methods from the world of secret messages in this FAQ list

### What is encryption and what is its purpose?

**Encryption** This is the name of the process in which human-readable text - but also information such as sound or image recordings - is converted into an "illegible" string. The readable text is called **Plain text**, the illegible, transformed text is the **Key text** or **Ciphertext**. The transformation itself is the actual encryption, the conversion takes place using mathematical processes. The reverse process, i.e. the conversion of the ciphertext back into the plaintext, is this **Decryption**.

The purpose of encryption is to hide information from unauthorized or unwanted viewing. This is especially the case when messages are to be transmitted from a sender to a recipient without a third party having to see this information.

### Is it possible to visualize encryption?

Yes. An example that is often used is the so-called **Caesar encryption** or **Caesar cipher**which the Roman emperor Julius Caesar (100-44 BC) is said to have used for his military correspondence, according to tradition. The Caesar cipher is a very simple letter replacement scheme: Each letter of the plaintext is transformed into a ciphertext letter by shifting each character of the message by a certain number to the right in the alphabet. For the last letters of the alphabet, the alphabet is repeated after Z. For decryption, the alphabet is shifted to the left by the same number of characters. In this case, the number of characters shifted forms the key.

You know the letter combination

"DQJULIILPPRUJHQJUDXHQ"

the key, the decryption is done quickly:

Key "Each letter is replaced by the third following in the alphabet."

*Clear:* a B C D E F G H I J K L M O P Q R S T U V w x y z

*Secret:* D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

The encrypted text therefore means in plain text: "Attack at dawn"

### What exactly is the term "key" all about?

The key is the central component for encrypting and decrypting a ciphertext. With Caesar encryption, the number of characters shifted forms the key.

Often the key is a **password**which is used to encrypt a plaintext and obtain a ciphertext. Conversely, this password is required again as a key in order to recover the plain text from the ciphertext by decryption. In the case of computer-based methods, however, the key is one **Bit sequence**.

The **Key length **is a crucial factor for the security of the encryption. Roughly speaking, the key length is the number of different possible keys. With a small key space, an attacker can simply try out all possible keys. If an attack is found against a method that is more efficient than the brute force method, i.e. trying out all possible keys, the method is considered broken. The key space must therefore be large enough to make such a brute force attack futile.

Caesar encryption is extremely insecure. There are only 26 different keys that can be tried out by hand very quickly. Thus, a Caesar encryption can easily be cracked without further knowledge or special attack methods through a completely exhaustive key search.

With computer-based encryption, the key length can be read from the number of bits (40 bits, 56 bits, 128 bits, 256 bits). As with a longer password, there are several combinations for a longer key. 128-bit encryption is a trillion times stronger than 40-bit encryption

### Is encryption an invention of the modern age or the computer age?

No. Humans have been encrypting messages since ancient times, see the example of the Caesar cipher above. The history of encryption technology can be roughly divided into three epochs. In the first epoch up to around 1900, encryption was largely carried out by hand with a pen and paper or with mechanical disks. In the second epoch, from around 1920 to 1970, special machines were used, and in the third, from around 1970, the computer took over the encryption.

A well-known example of a special second period encryption engine is the** ENIGMA machine**. It was used by the National Socialists in World War II to encrypt radio messages and was considered unbreakable on the German side. As is well known, however, the British around the mathematician Alan Turing managed to decipher large parts of the intercepted ENIGMA radio messages.

In principle, the development of encryption techniques mostly took place in the military. One side, the cryptographers, tried to encrypt their messages. The other side, the cryptanalyst, tried to decipher it. Today, research in the field of encryption is much broader.

### What are the scientific bases of encryption?

Most encryption methods rely on the difficulty of problems investigated in mathematical number theory. To put it loosely, encryption is based on the principle that some things in life are easy to do but difficult to undo. Dropping a vase from a height of ten meters is easy; However, gluing the vase back together from the broken pieces is almost impossible.

There are similar phenomena in the area of numbers: multiplying numbers together - even very large ones - is easy. But it is comparatively difficult to break down a product into its unknown factors, that is, to "factorize" it. For example, finding the divisors of 805963 is difficult. The larger a number, the more difficult it becomes **Factorization**Which, if the numbers are large enough, means that factorization would take thousands of years even on a supercomputer.

In practice, therefore, numbers with several hundred decimal places are used. With the most sophisticated methods and a lot of computational effort, you are now able to factorize just 130-digit numbers.

### What are the basic encryption methods?

Basically, a distinction can be made between symmetrical and asymmetrical encryption methods.

At **symmetrical method** encryption and decryption are carried out with the same key. To do this, the sender and recipient must agree on the secret key before use and have securely exchanged it. Caesar encryption uses only one key and is therefore a symmetrical procedure. Other symmetrical methods are AES and 3DES (see below) or one-time encryption (One-Time-Pad, OTP), in which a random key with at least the length of the message to be encrypted is used once.

The **asymmetric encryption** uses a key pair for each participant: one **public key**, the "**Public key**", and one **private key**, the "**Private key**". The public key is accessible to everyone, the private key remains private or secret.

The sender uses the recipient's public key for encryption and the recipient uses his secret private key for decryption. The asymmetry arises because data that has been encrypted with the public key of the key pair can only be decrypted with the secret key of the key pair.

In practice it looks like this: For example, if you want to receive a secret message by e-mail, you generate a key pair. Then you send the public key to everyone who wants to write you a message. It is almost impossible for an attacker to generate the corresponding duplicate key from a sufficiently long key within a reasonable period of time. The best-known asymmetric method is RSA (see below).

### What are the pros and cons of asymmetric versus symmetric encryption?

The most important disadvantage of symmetrical encryption methods is that the generated key is responsible for both the encryption and the subsequent decryption. If two people exchange encrypted messages with each other, both must have the same key. A protected channel must therefore be available when the key is exchanged. Since this is usually not the case, an enemy has a chance of intercepting the secret key during transmission.

The advantage of the asymmetrical procedure is precisely the increased security and convenience: private keys never have to be transferred or shown to anyone. Another important advantage of asymmetric encryption is the possibility of electronic signatures.

A disadvantage of asymmetric encryption is the high cost of encryption and decryption, which has a significant impact on speed: Symmetric encryption methods are generally faster than asymmetric methods, since the algorithm works significantly slower than that of symmetric methods, especially with large data sets.

### Where are asymmetric procedures used most often?

The properties of asymmetric cryptosystems make a wide range of applications possible. Asymmetric methods are used nowadays, for example, in e-mail traffic as well as in cryptographic protocols such as SSL / TLS. For example, the https protocol is used to a greater extent for secure communication between a web browser and a server. Another common area of application is the digital signature (see below).

### Where can symmetrical methods be used better?

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