Danger
This is a “Hazardous Materials” module. You should ONLY use it if you’re 100% absolutely sure that you know what you’re doing because this module is full of land mines, dragons, and dinosaurs with laser guns.
Message digests (Hashing)¶
-
class
cryptography.hazmat.primitives.hashes.
Hash
(algorithm, backend)[source]¶ A cryptographic hash function takes an arbitrary block of data and calculates a fixed-size bit string (a digest), such that different data results (with a high probability) in different digests.
This is an implementation of
HashContext
meant to be used withHashAlgorithm
implementations to provide an incremental interface to calculating various message digests.>>> from cryptography.hazmat.backends import default_backend >>> from cryptography.hazmat.primitives import hashes >>> digest = hashes.Hash(hashes.SHA256(), backend=default_backend()) >>> digest.update(b"abc") >>> digest.update(b"123") >>> digest.finalize() b'l\xa1=R\xcap\xc8\x83\xe0\xf0\xbb\x10\x1eBZ\x89\xe8bM\xe5\x1d\xb2\xd29%\x93\xafj\x84\x11\x80\x90'
If the backend doesn’t support the requested
algorithm
anUnsupportedAlgorithm
exception will be raised.Keep in mind that attacks against cryptographic hashes only get stronger with time, and that often algorithms that were once thought to be strong, become broken. Because of this it’s important to include a plan for upgrading the hash algorithm you use over time. For more information, see Lifetimes of cryptographic hash functions.
Parameters: - algorithm – A
HashAlgorithm
instance such as those described in below. - backend – A
HashBackend
instance.
Raises: cryptography.exceptions.UnsupportedAlgorithm – This is raised if the provided
backend
does not implementHashBackend
-
update
(data)[source]¶ Parameters: data (bytes) – The bytes to be hashed.
Raises: - cryptography.exceptions.AlreadyFinalized – See
finalize()
. - TypeError – This exception is raised if
data
is notbytes
.
- cryptography.exceptions.AlreadyFinalized – See
-
copy
()[source]¶ Copy this
Hash
instance, usually so that you may callfinalize()
to get an intermediate digest value while we continue to callupdate()
on the original instance.Returns: A new instance of Hash
that can be updated and finalized independently of the original instance.Raises: cryptography.exceptions.AlreadyFinalized – See finalize()
.
-
finalize
()[source]¶ Finalize the current context and return the message digest as bytes.
After
finalize
has been called this object can no longer be used andupdate()
,copy()
, andfinalize()
will raise anAlreadyFinalized
exception.Return bytes: The message digest as bytes.
- algorithm – A
SHA-2 family¶
-
class
cryptography.hazmat.primitives.hashes.
SHA224
[source]¶ SHA-224 is a cryptographic hash function from the SHA-2 family and is standardized by NIST. It produces a 224-bit message digest.
-
class
cryptography.hazmat.primitives.hashes.
SHA256
[source]¶ SHA-256 is a cryptographic hash function from the SHA-2 family and is standardized by NIST. It produces a 256-bit message digest.
BLAKE2¶
BLAKE2 is a cryptographic hash function specified in RFC 7693. BLAKE2’s design makes it immune to length-extension attacks, an advantage over the SHA-family of hashes.
Note
While the RFC specifies keying, personalization, and salting features, these are not supported at this time due to limitations in OpenSSL 1.1.0.
-
class
cryptography.hazmat.primitives.hashes.
BLAKE2b
(digest_size)[source]¶ BLAKE2b is optimized for 64-bit platforms and produces an 1 to 64-byte message digest.
Parameters: digest_size (int) – The desired size of the hash output in bytes. Only 64
is supported at this time.Raises: ValueError – If the digest_size
is invalid.
-
class
cryptography.hazmat.primitives.hashes.
BLAKE2s
(digest_size)[source]¶ BLAKE2s is optimized for 8 to 32-bit platforms and produces a 1 to 32-byte message digest.
Parameters: digest_size (int) – The desired size of the hash output in bytes. Only 32
is supported at this time.Raises: ValueError – If the digest_size
is invalid.
SHA-1¶
Warning
SHA-1 is a deprecated hash algorithm that has practical known collision attacks. You are strongly discouraged from using it. Existing applications should strongly consider moving away.
MD5¶
Warning
MD5 is a deprecated hash algorithm that has practical known collision attacks. You are strongly discouraged from using it. Existing applications should strongly consider moving away.
Interfaces¶
-
class
cryptography.hazmat.primitives.hashes.
HashContext
[source]¶ -
algorithm
¶ A
HashAlgorithm
that will be used by this context.
-
copy
()[source]¶ Returns: A HashContext
that is a copy of the current context.
-