Python Binding¶
New in version 1.11.14.
The Python binding is based on the ffi module of botan and the ctypes module of the Python standard library.
Starting in 2.8, the class names were renamed to match Python standard conventions. However aliases are defined which allow older code to continue to work; the older names are mentioned as “previously X”.
Versioning¶

botan.
version_major
()¶ Returns the major number of the library version.

botan.
version_minor
()¶ Returns the minor number of the library version.

botan.
version_patch
()¶ Returns the patch number of the library version.

botan.
version_string
()¶ Returns a free form version string for the library
Random Number Generators¶

class
botan.
RandomNumberGenerator
(rng_type = 'system')¶ Previously
rng
Type ‘user’ also allowed (userspace HKDF RNG seeded from system rng). The system RNG is very cheap to create, as just a single file handle or CSP handle is kept open, from first use until shutdown, no matter how many ‘system’ rng instances are created. Thus it is easy to use the RNG in a oneoff way, with botan.rng().get(32).

get
(length)¶ Return some bits

reseed
(bits = 256)¶ Meaningless on system RNG, on userspace RNG causes a reseed/rekey

reseed_from_rng
(source_rng, bits = 256)¶ Take bits from the source RNG and use it to seed
self

add_entropy
(seed)¶ Add some unpredictable seed data to the RNG

Hash Functions¶

class
botan.
HashFunction
(algo)¶ Previously
hash_function
Algo is a string (eg ‘SHA1’, ‘SHA384’, ‘Skein512’)

algo_name
()¶ Returns the name of this algorithm

clear
()¶ Clear state

output_length
()¶ Return output length in bytes

update
(x)¶ Add some input

final
()¶ Returns the hash of all input provided, resets for another message.

Message Authentication Codes¶

class
botan.
MsgAuthCode
(algo)¶ Previously
message_authentication_code
Algo is a string (eg ‘HMAC(SHA256)’, ‘Poly1305’, ‘CMAC(AES256)’)

algo_name
()¶ Returns the name of this algorithm

clear
()¶ Clear internal state including the key

output_length
()¶ Return the output length in bytes

set_key
(key)¶ Set the key

update
(x)¶ Add some input

final
()¶ Returns the MAC of all input provided, resets for another message with the same key.

Ciphers¶

class
botan.
SymmetricCipher
(object, algo, encrypt = True)¶ Previously
cipher
The algorithm is spcified as a string (eg ‘AES128/GCM’, ‘Serpent/OCB(12)’, ‘Threefish512/EAX’).
Set the second param to False for decryption

algo_name
()¶ Returns the name of this algorithm

tag_length
()¶ Returns the tag length (0 for unauthenticated modes)

default_nonce_length
()¶ Returns default nonce length

update_granularity
()¶ Returns update block size. Call to update() must provide input of exactly this many bytes

is_authenticated
()¶ Returns True if this is an AEAD mode

valid_nonce_length
(nonce_len)¶ Returns True if nonce_len is a valid nonce len for this mode

clear
()¶ Resets all state

set_key
(key)¶ Set the key

set_assoc_data
(ad)¶ Sets the associated data. Fails if this is not an AEAD mode

start
(nonce)¶ Start processing a message using nonce

update
(txt)¶ Consumes input text and returns output. Input text must be of update_granularity() length. Alternately, always call finish with the entire message, avoiding calls to update entirely

finish
(txt = None)¶ Finish processing (with an optional final input). May throw if message authentication checks fail, in which case all plaintext previously processed must be discarded. You may call finish() with the entire message

Bcrypt¶

botan.
bcrypt
(passwd, rng, work_factor = 10)¶ Provided the password and an RNG object, returns a bcrypt string

botan.
check_bcrypt
(passwd, bcrypt)¶ Check a bcrypt hash against the provided password, returning True iff the password matches.
PBKDF¶

botan.
pbkdf
(algo, password, out_len, iterations = 100000, salt = None)¶ Runs a PBKDF2 algo specified as a string (eg ‘PBKDF2(SHA256)’, ‘PBKDF2(CMAC(Blowfish))’). Runs with specified iterations, with meaning depending on the algorithm. The salt can be provided or otherwise is randomly chosen. In any case it is returned from the call.
Returns out_len bytes of output (or potentially less depending on the algorithm and the size of the request).
Returns tuple of salt, iterations, and psk

botan.
pbkdf_timed
(algo, password, out_len, ms_to_run = 300, salt = rng().get(12))¶ Runs for as many iterations as needed to consumed ms_to_run milliseconds on whatever we’re running on. Returns tuple of salt, iterations, and psk
Scrypt¶
New in version 2.8.0.

botan.
scrypt
(out_len, password, salt, N=1024, r=8, p=8)¶ Runs Scrypt key derivation function over the specified password and salt using Scrypt parameters N, r, p.
KDF¶

botan.
kdf
(algo, secret, out_len, salt)¶ Performs a key derviation function (such as “HKDF(SHA384)”) over the provided secret and salt values. Returns a value of the specified length.
Public Key¶

class
botan.
PublicKey
(object)¶ Previously
public_key

fingerprint
(hash = 'SHA256')¶ Returns a hash of the public key

algo_name
()¶ Returns the algorithm name

estimated_strength
()¶ Returns the estimated strength of this key against known attacks (NFS, Pollard’s rho, etc)

encoding
(pem=False)¶ Returns the encoding of the key, PEM if set otherwise DER

Private Key¶

class
botan.
PrivateKey
(algo, param, rng)¶ Previously
private_key
Constructor creates a new private key. The parameter type/value depends on the algorithm. For “rsa” is is the size of the key in bits. For “ecdsa” and “ecdh” it is a group name (for instance “secp256r1”). For “ecdh” there is also a special case for group “curve25519” (which is actually a completely distinct key type with a nonstandard encoding).

get_public_key
()¶
Return a public_key object

export
()¶

Public Key Operations¶
Multiple Precision Integers (MPI)¶
New in version 2.8.0.

class
botan.
MPI
(initial_value=None)¶ Initialize an MPI object with specified value, left as zero otherwise. The
initial_value
should be anint
,str
, orMPI
.Most of the usual arithmetic operators (
__add__
,__mul__
, etc) are defined.
inverse_mod
(modulus)¶ Return the inverse of
self
modulo modulus, or zero if no inverse exists

is_prime
(rng, prob=128)¶ Test if
self
is prime

pow_mod(exponent, modulus):
Return
self
to theexponent
power modulomodulus

Format Preserving Encryption (FE1 scheme)¶
New in version 2.8.0.

class
botan.
FormatPreservingEncryptionFE1
(modulus, key, rounds=5, compat_mode=False)¶ Initialize an instance for format preserving encryption

encrypt
(msg, tweak)¶ The msg should be a botan2.MPI or an object which can be converted to one

decrypt
(msg, tweak)¶ The msg should be a botan2.MPI or an object which can be converted to one

HOTP¶
New in version 2.8.0.

class
botan.
HOTP
(key, hash="SHA1", digits=6)¶ 
generate
(counter)¶ Generate an HOTP code for the provided counter

check
(code, counter, resync_range=0)¶ Check if provided
code
is the correct code forcounter
. Ifresync_range
is greater than zero, HOTP also checks up toresync_range
following counter values.Returns a tuple of (bool,int) where the boolean indicates if the code was valid, and the int indicates the next counter value that should be used. If the code did not verify, the next counter value is always identical to the counter that was passed in. If the code did verify and resync_range was zero, then the next counter will always be counter+1.
