Metadata-Version: 2.1
Name: ecdsa
Version: 0.18.0
Summary: ECDSA cryptographic signature library (pure python)
Home-page: http://github.com/tlsfuzzer/python-ecdsa
Author: Brian Warner
Author-email: [email protected]
License: MIT
Platform: UNKNOWN
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.6
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.3
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Classifier: Programming Language :: Python :: 3.11
Requires-Python: >=2.6, !=3.0.*, !=3.1.*, !=3.2.*
Description-Content-Type: text/markdown
License-File: LICENSE
Requires-Dist: six (>=1.9.0)
Provides-Extra: gmpy
Requires-Dist: gmpy ; extra == 'gmpy'
Provides-Extra: gmpy2
Requires-Dist: gmpy2 ; extra == 'gmpy2'
# Pure-Python ECDSA and ECDH
[](https://github.com/tlsfuzzer/python-ecdsa/actions?query=workflow%3A%22GitHub+CI%22+branch%3Amaster)
[](https://ecdsa.readthedocs.io/en/latest/?badge=latest)
[](https://coveralls.io/github/tlsfuzzer/python-ecdsa?branch=master)
[](https://lgtm.com/projects/g/tlsfuzzer/python-ecdsa/context:python)
[](https://lgtm.com/projects/g/tlsfuzzer/python-ecdsa/alerts/)
[](https://pypi.python.org/pypi/ecdsa/)
This is an easy-to-use implementation of ECC (Elliptic Curve Cryptography)
with support for ECDSA (Elliptic Curve Digital Signature Algorithm),
EdDSA (Edwards-curve Digital Signature Algorithm) and ECDH
(Elliptic Curve Diffie-Hellman), implemented purely in Python, released under
the MIT license. With this library, you can quickly create key pairs (signing
key and verifying key), sign messages, and verify the signatures. You can
also agree on a shared secret key based on exchanged public keys.
The keys and signatures are very short, making them easy to handle and
incorporate into other protocols.
**NOTE: This library should not be used in production settings, see [Security](#Security) for more details.**
## Features
This library provides key generation, signing, verifying, and shared secret
derivation for five
popular NIST "Suite B" GF(p) (_prime field_) curves, with key lengths of 192,
224, 256, 384, and 521 bits. The "short names" for these curves, as known by
the OpenSSL tool (`openssl ecparam -list_curves`), are: `prime192v1`,
`secp224r1`, `prime256v1`, `secp384r1`, and `secp521r1`. It includes the
256-bit curve `secp256k1` used by Bitcoin. There is also support for the
regular (non-twisted) variants of Brainpool curves from 160 to 512 bits. The
"short names" of those curves are: `brainpoolP160r1`, `brainpoolP192r1`,
`brainpoolP224r1`, `brainpoolP256r1`, `brainpoolP320r1`, `brainpoolP384r1`,
`brainpoolP512r1`. Few of the small curves from SEC standard are also
included (mainly to speed-up testing of the library), those are:
`secp112r1`, `secp112r2`, `secp128r1`, and `secp160r1`.
Key generation, siging and verifying is also supported for Ed25519 and
Ed448 curves.
No other curves are included, but it is not too hard to add support for more
curves over prime fields.
## Dependencies
This library uses only Python and the 'six' package. It is compatible with
Python 2.6, 2.7, and 3.3+. It also supports execution on alternative
implementations like pypy and pypy3.
If `gmpy2` or `gmpy` is installed, they will be used for faster arithmetic.
Either of them can be installed after this library is installed,
`python-ecdsa` will detect their presence on start-up and use them
automatically.
You should prefer `gmpy2` on Python3 for optimal performance.
To run the OpenSSL compatibility tests, the 'openssl' tool must be in your
`PATH`. This release has been tested successfully against OpenSSL 0.9.8o,
1.0.0a, 1.0.2f, 1.1.1d and 3.0.1 (among others).
## Installation
This library is available on PyPI, it's recommended to install it using `pip`:
```
pip install ecdsa
```
In case higher performance is wanted and using native code is not a problem,
it's possible to specify installation together with `gmpy2`:
```
pip install ecdsa[gmpy2]
```
or (slower, legacy option):
```
pip install ecdsa[gmpy]
```
## Speed
The following table shows how long this library takes to generate key pairs
(`keygen`), to sign data (`sign`), to verify those signatures (`verify`),
to derive a shared secret (`ecdh`), and
to verify the signatures with no key-specific precomputation (`no PC verify`).
All those values are in seconds.
For convenience, the inverses of those values are also provided:
how many keys per second can be generated (`keygen/s`), how many signatures
can be made per second (`sign/s`), how many signatures can be verified
per second (`verify/s`), how many shared secrets can be derived per second
(`ecdh/s`), and how many signatures with no key specific
precomputation can be verified per second (`no PC verify/s`). The size of raw
signature (generally the smallest
the way a signature can be encoded) is also provided in the `siglen` column.
Use `tox -e speed` to generate this table on your own computer.
On an Intel Core i7 4790K @ 4.0GHz I'm getting the following performance:
```
siglen keygen keygen/s sign sign/s verify verify/s no PC verify no PC verify/s
NIST192p: 48 0.00032s 3134.06 0.00033s 2985.53 0.00063s 1598.36 0.00129s 774.43
NIST224p: 56 0.00040s 2469.24 0.00042s 2367.88 0.00081s 1233.41 0.00170s 586.66
NIST256p: 64 0.00051s 1952.73 0.00054s 1867.80 0.00098s 1021.86 0.00212s 471.27
NIST384p: 96 0.00107s 935.92 0.00111s 904.23 0.00203s 491.77 0.00446s 224.00
NIST521p: 132 0.00210s 475.52 0.00215s 464.16 0.00398s 251.28 0.00874s 114.39
SECP256k1: 64 0.00052s 1921.54 0.00054s 1847.49 0.00105s 948.68 0.00210s 477.01
BRAINPOOLP160r1: 40 0.00025s 4003.88 0.00026s 3845.12 0.00053s 1893.93 0.00105s 949.92
BRAINPOOLP192r1: 48 0.00033s 3043.97 0.00034s 2975.98 0.00063s 1581.50 0.00135s 742.29
BRAINPOOLP224r1: 56 0.00041s 2436.44 0.00043s 2315.51 0.00078s 1278.49 0.00180s 556.16
BRAINPOOLP256r1: 64 0.00053s 1892.49 0.00054s 1846.24 0.00114s 875.64 0.00229s 437.25
BRAINPOOLP320r1: 80 0.00073s 1361.26 0.00076s 1309.25 0.00143s 699.29 0.00322s 310.49
BRAINPOOLP384r1: 96 0.00107s 931.29 0.00111s 901.80 0.00230s 434.19 0.00476s 210.20
BRAINPOOLP512r1: 128 0.00207s 483.41 0.00212s 471.42 0.00425s 235.43 0.00912s 109.61
SECP112r1: 28 0.00015s 6672.53 0.00016s 6440.34 0.00031s 3265.41 0.00056s 1774.20
SECP112r2: 28 0.00015s 6697.11 0.00015s 6479.98 0.00028s 3524.72 0.00058s 1716.16
SECP128r1: 32 0.00018s 5497.65 0.00019s 5272.89 0.00036s 2747.39 0.00072s 1396.16
SECP160r1: 42 0.00025s 3949.32 0.00026s 3894.45 0.00046s 2153.85 0.00102s 985.07
Ed25519: 64 0.00076s 1324.48 0.00042s 2405.01 0.00109s 918.05 0.00344s 290.50
Ed448: 114 0.00176s 569.53 0.00115s 870.94 0.00282s 355.04 0.01024s 97.69
ecdh ecdh/s
NIST192p: 0.00104s 964.89
NIST224p: 0.00134s 748.63
NIST256p: 0.00170s 587.08
NIST384p: 0.00352s 283.90
NIST521p: 0.00717s 139.51
SECP256k1: 0.00154s 648.40
BRAINPOOLP160r1: 0.00082s 1220.70
BRAINPOOLP192r1: 0.00105s 956.75
BRAINPOOLP224r1: 0.00136s 734.52
BRAINPOOLP256r1: 0.00178s 563.32
BRAINPOOLP320r1: 0.00252s 397.23
BRAINPOOLP384r1: 0.00376s 266.27
BRAINPOOLP512r1: 0.00733s 136.35
SECP112r1: 0.00046s 2180.40
SECP112r2: 0.00045s 2229.14
SECP128r1: 0.00054s 1868.15
SECP160r1: 0.00080s 1243.98
```
To test performance with `gmpy2` loaded, use `tox -e speedgmpy2`.
On the same machine I'm getting the following performance with `gmpy2`:
```
siglen keygen keygen/s sign sign/s verify verify/s no PC verify no PC verify/s
NIST192p: 48 0.00017s 5933.40 0.00017s 5751.70 0.00032s 3125.28 0.00067s 1502.41
NIST224p: 56 0.00021s 4782.87 0.00022s 4610.05 0.00040s 2487.04 0.00089s 1126.90
NIST256p: 64 0.00023s 4263.98 0.00024s 4125.16 0.00045s 2200.88 0.00098s 1016.82
NIST384p: 96 0.00041s 2449.54 0.00042s 2399.96 0.00083s 1210.57 0.00172s 581.43
NIST521p: 132 0.00071s 1416.07 0.00072s 1389.81 0.00144s 692.93 0.00312s 320.40
SECP256k1: 64 0.00024s 4245.05 0.00024s 4122.09 0.00045s 2206.40 0.00094s 1068.32
BRAINPOOLP160r1: 40 0.00014s 6939.17 0.00015s 6681.55 0.00029s 3452.43 0.00057s 1769.81
BRAINPOOLP192r1: 48 0.00017s 5920.05 0.00017s 5774.36 0.00034s 2979.00 0.00069s 1453.19
BRAINPOOLP224r1: 56 0.00021s 4732.12 0.00022s 4622.65 0.00041s 2422.47 0.00087s 1149.87
BRAINPOOLP256r1: 64 0.00024s 4233.02 0.00024s 4115.20 0.00047s 2143.27 0.00098s 1015.60
BRAINPOOLP320r1: 80 0.00032s 3162.38 0.00032s 3077.62 0.00063s 1598.83 0.00136s 737.34
BRAINPOOLP384r1: 96 0.00041s 2436.88 0.00042s 2395.62 0.00083s 1202.68 0.00178s 562.85
BRAINPOOLP512r1: 128 0.00063s 1587.60 0.00064s 1558.83 0.00125s 799.96 0.00281s 355.83
SECP112r1: 28 0.00009s 11118.66 0.00009s 10775.48 0.00018s 5456.00 0.00033s 3020.83
SECP112r2: 28 0.00009s 11322.97 0.00009s 10857.71 0.00017s 5748.77 0.00032s 3094.28
SECP128r1: 32 0.00010s 10078.39 0.00010s 9665.27 0.00019s 5200.58 0.00036s 2760.88
SECP160r1: 42 0.00015s 6875.51 0.00015s 6647.35 0.00029s 3422.41 0.00057s 1768.35
Ed25519: 64 0.00030s 3322.56 0.00018s 5568.63 0.00046s 2165.35 0.00153s 654.02
Ed448: 114 0.00060s 1680.53 0.00039s 2567.40 0.00096s 1036.67 0.00350s 285.62
ecdh ecdh/s
NIST192p: 0.00050s 1985.70
NIST224p: 0.00066s 1524.16
NIST256p: 0.00071s 1413.07
NIST384p: 0.00127s 788.89
NIST521p: 0.00230s 434.85
SECP256k1: 0.00071s 1409.95
BRAINPOOLP160r1: 0.00042s 2374.65
BRAINPOOLP192r1: 0.00051s 1960.01
BRAINPOOLP224r1: 0.00066s 1518.37
BRAINPOOLP256r1: 0.00071s 1399.90
BRAINPOOLP320r1: 0.00100s 997.21
BRAINPOOLP384r1: 0.00129s 777.51
BRAINPOOLP512r1: 0.00210s 475.99
SECP112r1: 0.00022s 4457.70
SECP112r2: 0.00024s 4252.33
SECP128r1: 0.00028s 3589.31
SECP160r1: 0.00043s 2305.02
```
(there's also `gmpy` version, execute it using `tox -e speedgmpy`)
For comparison, a highly optimised implementation (including curve-specific
assembly for some curves), like the one in OpenSSL 1.1.1d, provides the
following performance numbers on the same machine.
Run `openssl speed ecdsa` and `openssl speed ecdh` to reproduce it:
```
sign verify sign/s verify/s
192 bits ecdsa (nistp192) 0.0002s 0.0002s 4785.6 5380.7
224 bits ecdsa (nistp224) 0.0000s 0.0001s 22475.6 9822.0
256 bits ecdsa (nistp256) 0.0000s 0.0001s 45069.6 14166.6
384 bits ecdsa (nistp384) 0.0008s 0.0006s 1265.6 1648.1
521 bits ecdsa (nistp521) 0.0003s 0.0005s 3753.1 1819.5
256 bits ecdsa (brainpoolP256r1) 0.0003s 0.0003s 2983.5 3333.2
384 bits ecdsa (brainpoolP384r1) 0.0008s 0.0007s 1258.8 1528.1
512 bits ecdsa (brainpoolP512r1) 0.0015s 0.0012s 675.1 860.1
sign verify sign/s verify/s
253 bits EdDSA (Ed25519) 0.0000s 0.0001s 28217.9 10897.7
456 bits EdDSA (Ed448) 0.0003s 0.0005s 3926.5 2147.7
op op/s
192 bits ecdh (nistp192) 0.0002s 4853.4
224 bits ecdh (nistp224) 0.0001s 15252.1
256 bits ecdh (nistp256) 0.0001s 18436.3
384 bits ecdh (nistp384) 0.0008s 1292.7
521 bits ecdh (nistp521) 0.0003s 2884.7
256 bits ecdh (brainpoolP256r1) 0.0003s 3066.5
384 bits ecdh (brainpoolP384r1) 0.0008s 1298.0
512 bits ecdh (brainpoolP512r1) 0.0014s 694.8
```
Keys and signature can be serialized in different ways (see Usage, below).
For a NIST192p key, the three basic representations require strings of the
following lengths (in bytes):
to_string: signkey= 24, verifykey= 48, signature=48
compressed: signkey=n/a, verifykey= 25, signature=n/a
DER: signkey=106, verifykey= 80, signature=55
PEM: signkey=278, verifykey=162, (no support for PEM signatures)
## History
In 2006, Peter Pearson announced his pure-python implementation of ECDSA in a
[message to sci.crypt][1], available from his [download site][2]. In 2010,
Brian Warner wrote a wrapper around this code, to make it a bit easier and
safer to use. In 2020, Hubert Kario included an implementation of elliptic
curve cryptography that uses Jacobian coordinates internally, improving
performance about 20-fold. You are looking at the README for this wrapper.
[1]: http://www.derkeiler.com/Newsgroups/sci.crypt/2006-01/msg00651.html
[2]: http://webpages.charter.net/curryfans/peter/downloads.html
## Testing
To run the full test suite, do this:
tox -e coverage
On an Intel Core i7 4790K @ 4.0GHz, the tests take about 18 seconds to execute.
The test suite uses
[`hypothesis`](https://github.com/HypothesisWorks/hypothesis) so there is some
inherent variability in the test suite execution time.
One part of `test_pyecdsa.py` and `test_ecdh.py` checks compatibility with
OpenSSL, by running the "openssl" CLI tool, make sure it's in your `PATH` if
you want to test compatibility with it (if OpenSSL is missing, too old, or
doesn't support all the curves supported in upstream releases you will see
skipped tests in the above `coverage` run).
## Security
This library was not designed with security in mind. If you are processing
data that needs to be protected we suggest you use a quality wrapper around
OpenSSL. [pyca/cryptography](https://cryptography.io) is one example of such
a wrapper. The primary use-case of this library is as a portable library for
interoperability testing and as a teaching tool.
**This library does not protect against side-channel attacks.**
Do not allow attackers to measure how long it takes you to generate a key pair
or sign a message. Do not allow attackers to run code on the same physical
machine when key pair generation or signing is taking place (this includes
virtual machines). Do not allow attackers to measure how much power your
computer uses while generating the key pair or signing a message. Do not allow
attackers to measure RF interference coming from your computer while generating
a key pair or signing a message. Note: just loading the private key will cause
key pair generation. Other operations or attack vectors may also be
vulnerable to attacks. **For a sophisticated attacker observing just one
operation with a private key will be sufficient to completely
reconstruct the private key**.
Please also note that any Pure-python cryptographic library will be vulnerable
to the same side-channel attacks. This is because Python does not provide
side-channel secure primitives (with the exception of
[`hmac.compare_digest()`][3]), making side-channel secure programming
impossible.
This library depends upon a strong source of random numbers. Do not use it on
a system where `os.urandom()` does not provide cryptographically secure
random numbers.
[3]: https://docs.python.org/3/library/hmac.html#hmac.compare_digest
## Usage
You start by creating a `SigningKey`. You can use this to sign data, by passing
in data as a byte string and getting back the signature (also a byte string).
You can also ask a `SigningKey` to give you the corresponding `VerifyingKey`.
The `VerifyingKey` can be used to verify a signature, by passing it both the
data string and the signature byte string: it either returns True or raises
`BadSignatureError`.
```python
from ecdsa import SigningKey
sk = SigningKey.generate() # uses NIST192p
vk = sk.verifying_key
signature = sk.sign(b"message")
assert vk.verify(signature, b"message")
```
Each `SigningKey`/`VerifyingKey` is associated with a specific curve, like
NIST192p (the default one). Longer curves are more secure, but take longer to
use, and result in longer keys and signatures.
```python
from ecdsa import SigningKey, NIST384p
sk = SigningKey.generate(curve=NIST384p)
vk = sk.verifying_key
signature = sk.sign(b"message")
assert vk.verify(signature, b"message")
```
The `SigningKey` can be serialized into several different formats: the shortest
is to call `s=sk.to_string()`, and then re-create it with
`SigningKey.from_string(s, curve)` . This short form does not record the
curve, so you must be sure to pass to `from_string()` the same curve you used
for the original key. The short form of a NIST192p-based signing key is just 24
bytes long. If a point encoding is invalid or it does not lie on the specified
curve, `from_string()` will raise `MalformedPointError`.
```python
from ecdsa import SigningKey, NIST384p
sk = SigningKey.generate(curve=NIST384p)
sk_string = sk.to_string()
sk2 = SigningKey.from_string(sk_string, curve=NIST384p)
print(sk_string.hex())
print(sk2.to_string().hex())
```
Note: while the methods are called `to_string()` the type they return is
actually `bytes`, the "string" part is leftover from Python 2.
`sk.to_pem()` and `sk.to_der()` will serialize the signing key into the same
formats that OpenSSL uses. The PEM file looks like the familiar ASCII-armored
`"-----BEGIN EC PRIVATE KEY-----"` base64-encoded format, and the DER format
is a shorter binary form of the same data.
`SigningKey.from_pem()/.from_der()` will undo this serialization. These
formats include the curve name, so you do not need to pass in a curve
identifier to the deserializer. In case the file is malformed `from_der()`
and `from_pem()` will raise `UnexpectedDER` or` MalformedPointError`.
```python
from ecdsa import SigningKey, NIST384p
sk = SigningKey.generate(curve=NIST384p)
sk_pem = sk.to_pem()
sk2 = SigningKey.from_pem(sk_pem)
# sk and sk2 are the same key
```
Likewise, the `VerifyingKey` can be serialized in the same way:
`vk.to_string()/VerifyingKey.from_string()`, `to_pem()/from_pem()`, and
`to_der()/from_der()`. The same `curve=` argument is needed for
`VerifyingKey.from_string()`.
```python
from ecdsa import SigningKey, VerifyingKey, NIST384p
sk = SigningKey.generate(curve=NIST384p)
vk = sk.verifying_key
vk_string = vk.to_string()
vk2 = VerifyingKey.from_string(vk_string, curve=NIST384p)
# vk and vk2 are the same key
from ecdsa import SigningKey, VerifyingKey, NIST384p
sk = SigningKey.generate(curve=NIST384p)
vk = sk.verifying_key
vk_pem = vk.to_pem()
vk2 = VerifyingKey.from_pem(vk_pem)
# vk and vk2 are the same key
```
There are a couple of different ways to compute a signature. Fundamentally,
ECDSA takes a number that represents the data being signed, and returns a
pair of numbers that represent the signature. The `hashfunc=` argument to
`sk.sign()` and `vk.verify()` is used to turn an arbitrary string into a
fixed-length digest, which is then turned into a number that ECDSA can sign,
and both sign and verify must use the same approach. The default value is
`hashlib.sha1`, but if you use NIST256p or a longer curve, you can use
`hashlib.sha256` instead.
There are also multiple ways to represent a signature. The default
`sk.sign()` and `vk.verify()` methods present it as a short string, for
simplicity and minimal overhead. To use a different scheme, use the
`sk.sign(sigencode=)` and `vk.verify(sigdecode=)` arguments. There are helper
functions in the `ecdsa.util` module that can be useful here.
It is also possible to create a `SigningKey` from a "seed", which is
deterministic. This can be used in protocols where you want to derive
consistent signing keys from some other secret, for example when you want
three separate keys and only want to store a single master secret. You should
start with a uniformly-distributed unguessable seed with about `curve.baselen`
bytes of entropy, and then use one of the helper functions in `ecdsa.util` to
convert it into an integer in the correct range, and then finally pass it
into `SigningKey.from_secret_exponent()`, like this:
```python
import os
from ecdsa import NIST384p, SigningKey
from ecdsa.util import randrange_from_seed__trytryagain
def make_key(seed):
secexp = randrange_from_seed__trytryagain(seed, NIST384p.order)
return SigningKey.from_secret_exponent(secexp, curve=NIST384p)
seed = os.urandom(NIST384p.baselen) # or other starting point
sk1a = make_key(seed)
sk1b = make_key(seed)
# note: sk1a and sk1b are the same key
assert sk1a.to_string() == sk1b.to_string()
sk2 = make_key(b"2-"+seed) # different key
assert sk1a.to_string() != sk2.to_string()
```
In case the application will verify a lot of signatures made with a single
key, it's possible to precompute some of the internal values to make
signature verification significantly faster. The break-even point occurs at
about 100 signatures verified.
To perform precomputation, you can call the `precompute()` method
on `VerifyingKey` instance:
```python
from ecdsa import SigningKey, NIST384p
sk = SigningKey.generate(curve=NIST384p)
vk = sk.verifying_key
vk.precompute()
signature = sk.sign(b"message")
assert vk.verify(signature, b"message")
```
Once `precompute()` was called, all signature verifications with this key will
be faster to execute.
## OpenSSL Compatibility
To produce signatures that can be verified by OpenSSL tools, or to verify
signatures that were produced by those tools, use:
```python
# openssl ecparam -name prime256v1 -genkey -out sk.pem
# openssl ec -in sk.pem -pubout -out vk.pem
# echo "data for signing" > data
# openssl dgst -sha256 -sign sk.pem -out data.sig data
# openssl dgst -sha256 -verify vk.pem -signature data.sig data
# openssl dgst -sha256 -prverify sk.pem -signature data.sig data
import hashlib
from ecdsa import SigningKey, VerifyingKey
from ecdsa.util import sigencode_der, sigdecode_der
with open("vk.pem") as f:
vk = VerifyingKey.from_pem(f.read())
with open("data", "rb") as f:
data = f.read()
with open("data.sig", "rb") as f:
signature = f.read()
assert vk.verify(signature, data, hashlib.sha256, sigdecode=sigdecode_der)
with open("sk.pem") as f:
sk = SigningKey.from_pem(f.read(), hashlib.sha256)
new_signature = sk.sign_deterministic(data, sigencode=sigencode_der)
with open("data.sig2", "wb") as f:
f.write(new_signature)
# openssl dgst -sha256 -verify vk.pem -signature data.sig2 data
```
Note: if compatibility with OpenSSL 1.0.0 or earlier is necessary, the
`sigencode_string` and `sigdecode_string` from `ecdsa.util` can be used for
respectively writing and reading the signatures.
The keys also can be written in format that openssl can handle:
```python
from ecdsa import SigningKey, VerifyingKey
with open("sk.pem") as f:
sk = SigningKey.from_pem(f.read())
with open("sk.pem", "wb") as f:
f.write(sk.to_pem())
with open("vk.pem") as f:
vk = VerifyingKey.from_pem(f.read())
with open("vk.pem", "wb") as f:
f.write(vk.to_pem())
```
## Entropy
Creating a signing key with `SigningKey.generate()` requires some form of
entropy (as opposed to
`from_secret_exponent`/`from_string`/`from_der`/`from_pem`,
which are deterministic and do not require an entropy source). The default
source is `os.urandom()`, but you can pass any other function that behaves
like `os.urandom` as the `entropy=` argument to do something different. This
may be useful in unit tests, where you want to achieve repeatable results. The
`ecdsa.util.PRNG` utility is handy here: it takes a seed and produces a strong
pseudo-random stream from it:
```python
from ecdsa.util import PRNG
from ecdsa import SigningKey
rng1 = PRNG(b"seed")
sk1 = SigningKey.generate(entropy=rng1)
rng2 = PRNG(b"seed")
sk2 = SigningKey.generate(entropy=rng2)
# sk1 and sk2 are the same key
```
Likewise, ECDSA signature generation requires a random number, and each
signature must use a different one (using the same number twice will
immediately reveal the private signing key). The `sk.sign()` method takes an
`entropy=` argument which behaves the same as `SigningKey.generate(entropy=)`.
## Deterministic Signatures
If you call `SigningKey.sign_deterministic(data)` instead of `.sign(data)`,
the code will generate a deterministic signature instead of a random one.
This uses the algorithm from RFC6979 to safely generate a unique `k` value,
derived from the private key and the message being signed. Each time you sign
the same message with the same key, you will get the same signature (using
the same `k`).
This may become the default in a future version, as it is not vulnerable to
failures of the entropy source.
## Examples
Create a NIST192p key pair and immediately save both to disk:
```python
from ecdsa import SigningKey
sk = SigningKey.generate()
vk = sk.verifying_key
with open("private.pem", "wb") as f:
f.write(sk.to_pem())
with open("public.pem", "wb") as f:
f.write(vk.to_pem())
```
Load a signing key from disk, use it to sign a message (using SHA-1), and write
the signature to disk:
```python
from ecdsa import SigningKey
with open("private.pem") as f:
sk = SigningKey.from_pem(f.read())
with open("message", "rb") as f:
message = f.read()
sig = sk.sign(message)
with open("signature", "wb") as f:
f.write(sig)
```
Load the verifying key, message, and signature from disk, and verify the
signature (assume SHA-1 hash):
```python
from ecdsa import VerifyingKey, BadSignatureError
vk = VerifyingKey.from_pem(open("public.pem").read())
with open("message", "rb") as f:
message = f.read()
with open("signature", "rb") as f:
sig = f.read()
try:
vk.verify(sig, message)
print "good signature"
except BadSignatureError:
print "BAD SIGNATURE"
```
Create a NIST521p key pair:
```python
from ecdsa import SigningKey, NIST521p
sk = SigningKey.generate(curve=NIST521p)
vk = sk.verifying_key
```
Create three independent signing keys from a master seed:
```python
from ecdsa import NIST192p, SigningKey
from ecdsa.util import randrange_from_seed__trytryagain
def make_key_from_seed(seed, curve=NIST192p):
secexp = randrange_from_seed__trytryagain(seed, curve.order)
return SigningKey.from_secret_exponent(secexp, curve)
sk1 = make_key_from_seed("1:%s" % seed)
sk2 = make_key_from_seed("2:%s" % seed)
sk3 = make_key_from_seed("3:%s" % seed)
```
Load a verifying key from disk and print it using hex encoding in
uncompressed and compressed format (defined in X9.62 and SEC1 standards):
```python
from ecdsa import VerifyingKey
with open("public.pem") as f:
vk = VerifyingKey.from_pem(f.read())
print("uncompressed: {0}".format(vk.to_string("uncompressed").hex()))
print("compressed: {0}".format(vk.to_string("compressed").hex()))
```
Load a verifying key from a hex string from compressed format, output
uncompressed:
```python
from ecdsa import VerifyingKey, NIST256p
comp_str = '022799c0d0ee09772fdd337d4f28dc155581951d07082fb19a38aa396b67e77759'
vk = VerifyingKey.from_string(bytearray.fromhex(comp_str), curve=NIST256p)
print(vk.to_string("uncompressed").hex())
```
ECDH key exchange with remote party:
```python
from ecdsa import ECDH, NIST256p
ecdh = ECDH(curve=NIST256p)
ecdh.generate_private_key()
local_public_key = ecdh.get_public_key()
#send `local_public_key` to remote party and receive `remote_public_key` from remote party
with open("remote_public_key.pem") as e:
remote_public_key = e.read()
ecdh.load_received_public_key_pem(remote_public_key)
secret = ecdh.generate_sharedsecret_bytes()
```