nodemcu-firmware/docs/modules/crypto.md

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# crypto Module
| Since | Origin / Contributor | Maintainer | Source |
| :----- | :-------------------- | :---------- | :------ |
| 2019-01-13 | [Javier Peletier](https://github.com/jpeletier) | [Javier Peletier](https://github.com/jpeletier) | [crypto.c](../../../components/modules/crypto.c)|
The crypto module provides various functions for working with cryptographic algorithms.
This is work in progress, for now only a number of hashing functions are available:
* SHA1
* SHA256
* SHA224
* SHA512
* SHA384
* MD5
All except MD5 are enabled by default. To disable algorithms you don't need, find the "Crypto module hashing algorithms" under the NodeMCU modules section in menuconfig.
## crypto.new_hash()
Create a digest/hash object that can have any number of strings added to it. Object has `update` and `finalize` functions.
#### Syntax
`hashobj = crypto.new_hash(algo)`
#### Parameters
`algo` the hash algorithm to use, case insensitive string
#### Returns
Hasher object with `update` and `finalize` functions available.
#### Example
```lua
hashobj = crypto.new_hash("SHA1")
hashobj:update("FirstString"))
hashobj:update("SecondString"))
digest = hashobj:finalize()
print(encoder.toHex(digest))
```