mirror of
https://github.com/BLAKE3-team/BLAKE3
synced 2024-04-28 17:55:08 +02:00
C readme edits
This commit is contained in:
parent
004b39a350
commit
44fd9efbc2
78
c/README.md
78
c/README.md
|
@ -103,6 +103,25 @@ void blake3_hasher_init_keyed(
|
|||
Initialize a `blake3_hasher` in the keyed hashing mode. The key must be
|
||||
exactly 32 bytes.
|
||||
|
||||
```c
|
||||
void blake3_hasher_init_derive_key(
|
||||
blake3_hasher *self,
|
||||
const char *context);
|
||||
```
|
||||
|
||||
Initialize a `blake3_hasher` in the key derivation mode. The context
|
||||
string is given as an initialization parameter, and afterwards input key
|
||||
material should be given with `blake3_hasher_update`. The context string
|
||||
is a null-terminated C string which should be **hardcoded, globally
|
||||
unique, and application-specific**. The context string should not
|
||||
include any dynamic input like salts, nonces, or identifiers read from a
|
||||
database at runtime. A good default format for the context string is
|
||||
`"[application] [commit timestamp] [purpose]"`, e.g., `"example.com
|
||||
2019-12-25 16:18:03 session tokens v1"`.
|
||||
|
||||
This function is intended for application code written in C. For
|
||||
language bindings, see `blake3_hasher_init_derive_key_raw` below.
|
||||
|
||||
```c
|
||||
void blake3_hasher_init_derive_key_raw(
|
||||
blake3_hasher *self,
|
||||
|
@ -110,29 +129,16 @@ void blake3_hasher_init_derive_key_raw(
|
|||
size_t context_len);
|
||||
```
|
||||
|
||||
Initialize a `blake3_hasher` in the key derivation mode. Key material
|
||||
is to be given as input after initialization, using
|
||||
`blake3_hasher_update`. The key derivation `context`
|
||||
should follow the __Key Derivation Context Guidelines__
|
||||
described below. `context_len` indicates the size of `context` in bytes.
|
||||
As `blake3_hasher_init_derive_key` above, except that the context string
|
||||
is given as a pointer to an array of arbitrary bytes with a provided
|
||||
length. This is intended for writing language bindings, where C string
|
||||
conversion would add unnecessary overhead and new error cases. Unicode
|
||||
strings should be encoded as UTF-8.
|
||||
|
||||
```c
|
||||
void blake3_hasher_init_derive_key(
|
||||
blake3_hasher *self,
|
||||
const char *context);
|
||||
```
|
||||
|
||||
Similar to `blake3_hasher_init_derive_key_raw`, except it takes the key
|
||||
derivation `context` as a null-terminated C string.
|
||||
|
||||
This function is offered as a convenience. It is recommended to use this
|
||||
function when giving a literal, hardcoded C string as parameter.
|
||||
|
||||
Notice that contrary to `blake3_hasher_init_derive_key_raw`, this function
|
||||
cannot accept `context`s containing the byte `0x00` except as a the
|
||||
terminating byte. For this reason, `blake3_hasher_init_derive_key_raw` is
|
||||
preferred in more general contexts, such as when implementing bindings to
|
||||
this C library.
|
||||
Application code in C should prefer `blake3_hasher_init_derive_key`,
|
||||
which takes the context as a C string. If you need to use arbitrary
|
||||
bytes as a context string in application code, consider whether you're
|
||||
violating the requirement that context strings should be hardcoded.
|
||||
|
||||
```c
|
||||
void blake3_hasher_finalize_seek(
|
||||
|
@ -147,34 +153,6 @@ parameter for the starting byte position in the output stream. To
|
|||
efficiently stream a large output without allocating memory, call this
|
||||
function in a loop, incrementing `seek` by the output length each time.
|
||||
|
||||
## Key Derivation Context Guidelines
|
||||
|
||||
The key derivation context should uniquely describe the
|
||||
application, place and purpose of the derivation.
|
||||
|
||||
The context should be **statically known,
|
||||
hardcoded, globally unique, and application-specific**.
|
||||
|
||||
The context should not depend on any dynamic input such as salts,
|
||||
nonces, or identifiers read from a database at runtime.
|
||||
|
||||
A good format for the context string is:
|
||||
|
||||
```
|
||||
[application] [commit timestamp] [purpose]
|
||||
```
|
||||
|
||||
For example:
|
||||
|
||||
```
|
||||
example.com 2019-12-25 16:18:03 session tokens v1
|
||||
```
|
||||
|
||||
It's recommended that the context string consists of ASCII bytes
|
||||
containing only alphanumeric characters, whitespace and punctuation.
|
||||
However, any bytes are acceptable as long as they satisfy the
|
||||
static constraints described above.
|
||||
|
||||
# Building
|
||||
|
||||
This implementation is just C and assembly files. It doesn't include a
|
||||
|
|
Loading…
Reference in New Issue