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Business type: BlockCypher

BlockCypher.

Secure file transfer protocols like SFTP, FTPS, HTTPS, and WebDAVS encrypt data through symmetric key ciphers. These ciphers can be classified into two groups: stream ciphers and block ciphers. Today, we'll discuss what a stream cipher is and what a block cipher is. We'll also talk about the popular encryption algorithms that fall under each group.


What is a block cipher? A block cipher is an encryption algorithm that encrypts a fixed size of n-bits of data - known as a block - at one time. The usual sizes of each block are 64 bits, 128 bits, and 256 bits. So for example, a 64-bit block cipher will take in 64 bits of plaintext and encrypt it into 64 bits of ciphertext. In cases where bits of plaintext is shorter than the block size, padding schemes are called into play. Majority of the symmetric ciphers used today are actually block ciphers. DES, Triple DES, AES, IDEA, and Blowfish are some of the commonly used encryption algorithms that fall under this group. Popular block ciphers DES - DES, which stands for Data Encryption Standard, used to be the most popular block cipher in the world and was used in several industries. It's still popular today, but only because it's usually included in historical discussions of encryption algorithms. The DES algorithm became a standard in the US in 1977. However, it's already been proven to be vulnerable to brute force attacks and other cryptanalytic methods. DES is a 64-bit cipher that works with a 64-bit key. Actually, 8 of the 64 bits in the key are parity bits, so the key size is technically 56 bits long. 3DES - As its name implies, 3DES is a cipher based on DES. It's practically DES that's run three times. Each DES operation can use a different key, with each key being 56 bits long. Like DES, 3DES has a block size of 64 bits. Although 3DES is many times stronger than DES, it is also much slower (about 3x slower). Because many organizations found 3DES to be too slow for many applications, it never became the ultimate successor of DES. That distinction is reserved for the next cipher in our list - AES. AES - A US Federal Government standard since 2002, AES or Advanced Encryption Standard is arguably the most widely used block cipher in the world. It has a block size of 128 bits and supports three possible key sizes - 128, 192, and 256 bits. The longer the key size, the stronger the encryption. However, longer keys also result in longer processes of encryption. For a discussion on encryption key lengths, read Choosing Key Lengths for Encrypted File Transfers. Blowfish - This is another popular block cipher (although not as widely used as AES). It has a block size of 64 bits and supports a variable-length key that can range from 32 to 448 bits. One thing that makes blowfish so appealing is that Blowfish is unpatented and royalty-free. Twofish - Yes, this cipher is related to Blowfish but it's not as popular (yet). It's a 128-bit block cipher that supports key sizes up to 256 bits long.