embit/docs/api/hashes.md

Hash functions

One-line variants of the common Bitcoin hash functions. For convenience.

API is common - pass a bytes object and get a hash of it.

Functions:

• sha256(msg)
• double_sha256(msg) - same as sha256(sha256(msg))
• ripemd160(msg)
• hash160(msg) - same as ripemd160(sha256(msg))
• tagged_hash(tag, data) - taproot hash function. tag is a string, data is bytes. It's basically sha256(sha256(tag) + sha256(tag) + data)

Tagged hash helper function:

• tagged_hash_init(tag, data) - initializes the tagged hash and returns a hash object that can be updated with more data.

Example

from embit import hashes

hashes.sha256(b"I'm sha256")
hashes.ripemd160("Hash me gently".encode())

hashes.tagged_hash("TapMessage", b"Taproot is coming!")

h = hashes.tagged_hash_init("TapMessage", b"Taproot")
h.update(b" is coming!")
result = h.digest()

sha256(msg)

Hashes a message using SHA-256 algorithm.

Arguments

• msg - bytes to hash

Returns

32-byte hash of the message

double_sha256(msg)

Hashes a message twice using SHA-256 algorithm.

Arguments

• msg - bytes to hash

Returns

32-byte hash of the message

ripemd160(msg)

Hashes a message using RIPEMD-160 algorithm.

Arguments

• msg - bytes to hash

Returns

20-byte hash of the message

hash160(msg)

Hashes a message using SHA-256 algorithm and then using RIPEMD-160.

Arguments

• msg - bytes to hash

Returns

20-byte hash of the message

tagged_hash(tag, msg)

Hashes a message with a tag using tagged hash defined in taproot update add ref.

Different tags are used for different application, for example in taproot "BIP0340/nonce" is used for nonce generation, "BIP0340/challenge" for signing etc.

This allows reusing of the hash function without worrying about getting the same hashes for different applications.

Internaly does sha256(sha256(tag) + sha256(tag) + data)

Arguments

• tag - a tag string uniquie for your application.
• msg - bytes to hash

Returns

32-byte hash of the message.

tagged_hash_init(tag, msg=b"")

Initializes a tagged hash object for more data.

Arguments

• tag - a tag string uniquie for your application
• msg - first bytes to hash, b"" by default

Retuns

a hash object that can be used to .update() with more data and digest() at the end.

After digest() the result will be 32-bytes.

Example

from embit import hashes

h = hashes.tagged_hash_init("TapMessage", b"Taproot")
h.update(b" is coming!")
result = h.digest()