nodemcu-firmware/docs/en/modules/crypto.md

crypto Module

The crypto modules provides various functions for working with cryptographic algorithms.

crypto.hash()

Compute a cryptographic hash of a Lua string.

Syntax

hash = crypto.hash(algo, str)

Parameters

algo the hash algorithm to use, case insensitive string

Supported hash algorithms are:

• MD2 (not available by default, has to be explicitly enabled in app/include/user_config.h)
• MD5
• SHA1
• SHA256, SHA384, SHA512 (unless disabled in app/include/user_config.h)

Returns

A binary string containing the message digest. To obtain the textual version (ASCII hex characters), please use crypto.toHex().

Example

print(crypto.toHex(crypto.hash("sha1","abc")))

crypto.hmac()

Compute a HMAC (Hashed Message Authentication Code) signature for a Lua string.

Syntax

signature = crypto.hmac(algo, str, key)

Parameters

• algo hash algorithm to use, case insensitive string
• str data to calculate the hash for
• key key to use for signing, may be a binary string

Supported hash algorithms are:

• MD2 (not available by default, has to be explicitly enabled in app/include/user_config.h)
• MD5
• SHA1
• SHA256, SHA384, SHA512 (unless disabled in app/include/user_config.h)

Returns

A binary string containing the HMAC signature. Use crypto.toHex() to obtain the textual version.

Example

print(crypto.toHex(crypto.hmac("sha1","abc","mysecret")))

crypto.mask()

Applies an XOR mask to a Lua string. Note that this is not a proper cryptographic mechanism, but some protocols may use it nevertheless.

Syntax

crypto.mask(message, mask)

Parameters

• message message to mask
• mask the mask to apply, repeated if shorter than the message

Returns

The masked message, as a binary string. Use crypto.toHex() to get a textual representation of it.

Example

print(crypto.toHex(crypto.mask("some message to obscure","X0Y7")))

crypto.toBase64()

Provides a Base64 representation of a (binary) Lua string.

Syntax

b64 = crypto.toBase64(binary)

Parameters

binary input string to Base64 encode

Return

A Base64 encoded string.

Example

print(crypto.toBase64(crypto.hash("sha1","abc")))

crypto.toHex()

Provides an ASCII hex representation of a (binary) Lua string. Each byte in the input string is represented as two hex characters in the output.

Syntax

hexstr = crypto.toHex(binary)

Parameters

binary input string to get hex representation for

Returns

An ASCII hex string.

Example

print(crypto.toHex(crypto.hash("sha1","abc")))