Usually HD wallets like Coinomi are used to take backup of multiple cryptos. A mnemonic code or sentence is superior for human interaction compared to the handling of raw binary or hexadecimal representations of a wallet seed.
Generating the mnemonic
The mnemonic must encode entropy in a multiple of 32 bits. With more entropy security is improved but the sentence length increases. We refer to the initial entropy length as ENT. The allowed size of ENT is 128-256 bits.
First, an initial entropy of ENT bits is generated. A checksum is generated by taking the first
ENT / 32
bits of its SHA256 hash. This checksum is appended to the end of the initial entropy. Next, these concatenated bits are split into groups of 11 bits, each encoding a number from 0-2047, serving as an index into a wordlist. Finally, we convert these numbers into words and use the joined words as a mnemonic sentence.
The following table describes the relation between the initial entropy length (ENT), the checksum length (CS) and the length of the generated mnemonic sentence (MS) in words.
CS = ENT / 32
MS = (ENT + CS) / 11
| ENT | CS | ENT+CS | MS |
| 128 | 4 | 132 | 12 |
| 160 | 5 | 165 | 15 |
| 192 | 6 | 198 | 18 |
| 224 | 7 | 231 | 21 |
| 256 | 8 | 264 | 24 |