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”. These aliases will be removed in a future major release.
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 HMAC_DRBG 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.RandomNumberGenerator().get(32).

get
(length)¶ Return some bytes

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
The
algo
param is a string (eg ‘SHA1’, ‘SHA384’, ‘BLAKE2b’)
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

classmethod
load
(val)¶ Load a public key. The value should be a PEM or DER blob.

classmethod
load_rsa
(n, e)¶ Load an RSA public key giving the modulus and public exponent as integers.

classmethod
load_dsa
(p, q, g, y)¶ Load an DSA public key giving the parameters and public value as integers.

classmethod
load_dh
(p, g, y)¶ Load an DiffieHellman public key giving the parameters and public value as integers.

classmethod
load_elgamal
(p, q, g, y)¶ Load an ElGamal public key giving the parameters and public value as integers.

classmethod
load_ecdsa
(curve, pub_x, pub_y)¶ Load an ECDSA public key giving the curve as a string (like “secp256r1”) and the public point as a pair of integers giving the affine coordinates.

classmethod
load_ecdh
(curve, pub_x, pub_y)¶ Load an ECDH public key giving the curve as a string (like “secp256r1”) and the public point as a pair of integers giving the affine coordinates.

classmethod
load_sm2
(curve, pub_x, pub_y)¶ Load a SM2 public key giving the curve as a string (like “sm2p256v1”) and the public point as a pair of integers giving the affine coordinates.

check_key(rng_obj, strong=True):
Test the key for consistency. If
strong
isTrue
then more expensive tests are performed.

export
(pem=False)¶ Exports the public key using the usual X.509 SPKI representation. If
pem
is True, the result is a PEM encoded string. Otherwise it is a binary DER value.

to_der
()¶ Like
self.export(False)

to_pem
()¶ Like
self.export(True)

get_field
(field_name)¶ Return an integer field related to the public key. The valid field names vary depending on the algorithm. For example RSA public modulus can be extracted with
rsa_key.get_field("n")
.

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)

classmethod
Private Key¶

class
botan.
PrivateKey
¶ Previously
private_key

classmethod
create
(algo, param, rng)¶ 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).

classmethod
load
(val, passphrase="")¶ Return a private key (DER or PEM formats accepted)

classmethod
load_rsa
(p, q, e)¶ Return a private RSA key

classmethod
load_dsa
(p, q, g, x)¶ Return a private DSA key

classmethod
load_dh
(p, g, x)¶ Return a private DH key

classmethod
load_elgamal
(p, q, g, x)¶ Return a private ElGamal key

classmethod
load_ecdsa
(curve, x)¶ Return a private ECDSA key

classmethod
load_ecdh
(curve, x)¶ Return a private ECDH key

classmethod
load_sm2
(curve, x)¶ Return a private SM2 key

get_public_key
()¶ Return a public_key object

to_pem
()¶ Return the PEM encoded private key (unencrypted)

to_der
()¶ Return the PEM encoded private key (unencrypted)

check_key(rng_obj, strong=True):
Test the key for consistency. If
strong
isTrue
then more expensive tests are performed.

algo_name
()¶ Returns the algorithm name

export
(pem=False)¶ Exports the private key in PKCS8 format. If
pem
is True, the result is a PEM encoded string. Otherwise it is a binary DER value. The key will not be encrypted.

export_encrypted
(passphrase, rng, pem=False, msec=300, cipher=None, pbkdf=None)¶ Exports the private key in PKCS8 format, encrypted using the provided passphrase. If
pem
is True, the result is a PEM encoded string. Otherwise it is a binary DER value.

to_der
() Like
self.export(False)

to_pem
() Like
self.export(True)

get_field
(field_name)¶ Return an integer field related to the public key. The valid field names vary depending on the algorithm. For example first RSA secret prime can be extracted with
rsa_key.get_field("p")
. This function can also be used to extract the public parameters.

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

class
botan.
MPI
(initial_value=None, radix=None)¶ Initialize an MPI object with specified value, left as zero otherwise. The
initial_value
should be anint
,str
, orMPI
. Theradix
value should be set to 16 when initializing from a base 16 str value.Most of the usual arithmetic operators (
__add__
,__mul__
, etc) are defined.
inverse_mod
(modulus)¶ Return the inverse of
self
modulomodulus
, 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

mod_mul(other, modulus):
Return the multiplication product of
self
andother
modulomodulus

gcd(other):
Return the greatest common divisor of
self
andother

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.

X509Cert¶

class
botan.
X509Cert
(filename=None, buf=None)¶ 
time_starts
()¶ Return the time the certificate becomes valid, as a string in form “YYYYMMDDHHMMSSZ” where Z is a literal character reflecting that this time is relative to UTC.

time_expires
()¶ Return the time the certificate expires, as a string in form “YYYYMMDDHHMMSSZ” where Z is a literal character reflecting that this time is relative to UTC.

to_string
()¶ Format the certificate as a freeform string.

fingerprint
(hash_algo='SHA256')¶ Return a fingerprint for the certificate, which is basically just a hash of the binary contents. Normally SHA1 or SHA256 is used, but any hash function is allowed.

serial_number
()¶ Return the serial number of the certificate.
Return the authority key ID set in the certificate, which may be empty.

subject_key_id
()¶ Return the subject key ID set in the certificate, which may be empty.

subject_public_key_bits
()¶ Get the serialized representation of the public key included in this certificate.

subject_public_key
()¶ Get the public key included in this certificate as an object of class
PublicKey
.

subject_dn
(key, index)¶ Get a value from the subject DN field.
key
specifies a value to get, for instance"Name"
or “Country”.

issuer_dn
(key, index)¶ Get a value from the issuer DN field.
key
specifies a value to get, for instance"Name"
or “Country”.

hostname_match
(hostname)¶ Return True if the Common Name (CN) field of the certificate matches a given
hostname
.

not_before
()¶ Return the time the certificate becomes valid, as seconds since epoch.

not_after
()¶ Return the time the certificate expires, as seconds since epoch.

allowed_usage
(usage_list)¶ Return True if the certificates Key Usage extension contains all constraints given in
usage_list
. Also return True if the certificate doesn’t have this extension. Example usage constraints are:"DIGITAL_SIGNATURE"
,"KEY_CERT_SIGN"
,"CRL_SIGN"
.

verify
(intermediates=None, trusted=None, trusted_path=None, required_strength=0, hostname=None, reference_time=0 crls=None)¶ Verify a certificate. Returns 0 if validation was successful, returns a positive error code if the validation was unsuccesful.
intermediates
is a list of untrusted subauthorities.trusted
is a list of trusted root CAs.The trusted_path refers to a directory where one or more trusted CA certificates are stored.
Set
required_strength
to indicate the minimum key and hash strength that is allowed. For instance setting to 80 allows 1024bit RSA and SHA1. Setting to 110 requires 2048bit RSA and SHA256 or higher. Set to zero to accept a default.If
hostname
is given, it will be checked against the certificates CN field.Set
reference_time
to be the time which the certificate chain is validated against. Use zero (default) to use the current system clock.crls
is a list of CRLs issued by either trusted or untrusted authorities.

classmethod
validation_status
(error_code)¶ Return an informative string associated with the verification return code.

is_revoked
(self, crl)¶ Check if the certificate (
self
) is revoked on the givencrl
.
