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| 1 .. _hashlib-blake2: |
| 2 |
| 3 :mod:`hashlib` --- BLAKE2 hash functions |
| 4 ======================================== |
| 5 |
| 6 .. module:: hashlib |
| 7 :synopsis: BLAKE2 hash function for Python |
| 8 .. sectionauthor:: Dmitry Chestnykh |
| 9 |
| 10 .. index:: |
| 11 single: blake2b, blake2s |
| 12 |
| 13 BLAKE2_ is a cryptographic hash function, which offers highest security while |
| 14 being as fast as MD5 or SHA-1, and comes in two flavors: |
| 15 |
| 16 * **BLAKE2b**, optimized for 64-bit platforms and produces digests of any size |
| 17 between 1 and 64 bytes, |
| 18 |
| 19 * **BLAKE2s**, optimized for 8- to 32-bit platforms and produces digests of any |
| 20 size between 1 and 32 bytes. |
| 21 |
| 22 BLAKE2 supports **keyed mode** (a faster and simpler replacement for HMAC_), |
| 23 **salted hashing**, **personalization**, and **tree hashing**. |
| 24 |
| 25 Hash objects from this module follow the API of standard library's |
| 26 :mod:`hashlib` objects. |
| 27 |
| 28 |
| 29 Module |
| 30 ====== |
| 31 |
| 32 Creating hash objects |
| 33 --------------------- |
| 34 |
| 35 New hash objects are created by calling constructor functions: |
| 36 |
| 37 |
| 38 .. function:: blake2b(data=b'', digest_size=64, key=b'', salt=b'', \ |
| 39 person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, \ |
| 40 node_depth=0, inner_size=0, last_node=False) |
| 41 |
| 42 .. function:: blake2s(data=b'', digest_size=32, key=b'', salt=b'', \ |
| 43 person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, \ |
| 44 node_depth=0, inner_size=0, last_node=False) |
| 45 |
| 46 |
| 47 These functions return the corresponding hash objects for calculating |
| 48 BLAKE2b or BLAKE2s. They optionally take these general parameters: |
| 49 |
| 50 * *data*: initial chunk of data to hash, which must be interpretable as buffer |
| 51 of bytes. |
| 52 |
| 53 * *digest_size*: size of output digest in bytes. |
| 54 |
| 55 * *key*: key for keyed hashing (up to 64 bytes for BLAKE2b, up to 32 bytes for |
| 56 BLAKE2s). |
| 57 |
| 58 * *salt*: salt for randomized hashing (up to 16 bytes for BLAKE2b, up to 8 |
| 59 bytes for BLAKE2s). |
| 60 |
| 61 * *person*: personalization string (up to 16 bytes for BLAKE2b, up to 8 bytes |
| 62 for BLAKE2s). |
| 63 |
| 64 The following table shows limits for general parameters (in bytes): |
| 65 |
| 66 ======= =========== ======== ========= =========== |
| 67 Hash digest_size len(key) len(salt) len(person) |
| 68 ======= =========== ======== ========= =========== |
| 69 BLAKE2b 64 64 16 16 |
| 70 BLAKE2s 32 32 8 8 |
| 71 ======= =========== ======== ========= =========== |
| 72 |
| 73 .. note:: |
| 74 |
| 75 BLAKE2 specification defines constant lengths for salt and personalization |
| 76 parameters, however, for convenience, this implementation accepts byte |
| 77 strings of any size up to the specified length. If the length of the |
| 78 parameter is less than specified, it is padded with zeros, thus, for |
| 79 example, ``b'salt'`` and ``b'salt\x00'`` is the same value. (This is not |
| 80 the case for *key*.) |
| 81 |
| 82 These sizes are available as module `constants`_ described below. |
| 83 |
| 84 Constructor functions also accept the following tree hashing parameters: |
| 85 |
| 86 * *fanout*: fanout (0 to 255, 0 if unlimited, 1 in sequential mode). |
| 87 |
| 88 * *depth*: maximal depth of tree (1 to 255, 255 if unlimited, 1 in |
| 89 sequential mode). |
| 90 |
| 91 * *leaf_size*: maximal byte length of leaf (0 to 2**32-1, 0 if unlimited or in |
| 92 sequential mode). |
| 93 |
| 94 * *node_offset*: node offset (0 to 2**64-1 for BLAKE2b, 0 to 2**48-1 for |
| 95 BLAKE2s, 0 for the first, leftmost, leaf, or in sequential mode). |
| 96 |
| 97 * *node_depth*: node depth (0 to 255, 0 for leaves, or in sequential mode). |
| 98 |
| 99 * *inner_size*: inner digest size (0 to 64 for BLAKE2b, 0 to 32 for |
| 100 BLAKE2s, 0 in sequential mode). |
| 101 |
| 102 * *last_node*: boolean indicating whether the processed node is the last |
| 103 one (`False` for sequential mode). |
| 104 |
| 105 .. figure:: hashlib-blake2-tree.png |
| 106 :alt: Explanation of tree mode parameters. |
| 107 |
| 108 See section 2.10 in `BLAKE2 specification |
| 109 <https://blake2.net/blake2_20130129.pdf>`_ for comprehensive review of tree |
| 110 hashing. |
| 111 |
| 112 |
| 113 Constants |
| 114 --------- |
| 115 |
| 116 .. data:: blake2b.SALT_SIZE |
| 117 .. data:: blake2s.SALT_SIZE |
| 118 |
| 119 Salt length (maximum length accepted by constructors). |
| 120 |
| 121 |
| 122 .. data:: blake2b.PERSON_SIZE |
| 123 .. data:: blake2s.PERSON_SIZE |
| 124 |
| 125 Personalization string length (maximum length accepted by constructors). |
| 126 |
| 127 |
| 128 .. data:: blake2b.MAX_KEY_SIZE |
| 129 .. data:: blake2s.MAX_KEY_SIZE |
| 130 |
| 131 Maximum key size. |
| 132 |
| 133 |
| 134 .. data:: blake2b.MAX_DIGEST_SIZE |
| 135 .. data:: blake2s.MAX_DIGEST_SIZE |
| 136 |
| 137 Maximum digest size that the hash function can output. |
| 138 |
| 139 |
| 140 Examples |
| 141 ======== |
| 142 |
| 143 Simple hashing |
| 144 -------------- |
| 145 |
| 146 To calculate hash of some data, you should first construct a hash object by |
| 147 calling the appropriate constructor function (:func:`blake2b` or |
| 148 :func:`blake2s`), then update it with the data by calling :meth:`update` on the |
| 149 object, and, finally, get the digest out of the object by calling |
| 150 :meth:`digest` (or :meth:`hexdigest` for hex-encoded string). |
| 151 |
| 152 >>> from hashlib import blake2b |
| 153 >>> h = blake2b() |
| 154 >>> h.update(b'Hello world') |
| 155 >>> h.hexdigest() |
| 156 '6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551
134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183' |
| 157 |
| 158 |
| 159 As a shortcut, you can pass the first chunk of data to update directly to the |
| 160 constructor as the first argument (or as *data* keyword argument): |
| 161 |
| 162 >>> from hashlib import blake2b |
| 163 >>> blake2b(b'Hello world').hexdigest() |
| 164 '6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551
134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183' |
| 165 |
| 166 You can call :meth:`hash.update` as many times as you need to iteratively |
| 167 update the hash: |
| 168 |
| 169 >>> from hashlib import blake2b |
| 170 >>> items = [b'Hello', b' ', b'world'] |
| 171 >>> h = blake2b() |
| 172 >>> for item in items: |
| 173 ... h.update(item) |
| 174 >>> h.hexdigest() |
| 175 '6ff843ba685842aa82031d3f53c48b66326df7639a63d128974c5c14f31a0f33343a8c65551
134ed1ae0f2b0dd2bb495dc81039e3eeb0aa1bb0388bbeac29183' |
| 176 |
| 177 |
| 178 Using different digest sizes |
| 179 ---------------------------- |
| 180 |
| 181 BLAKE2 has configurable size of digests up to 64 bytes for BLAKE2b and up to 32 |
| 182 bytes for BLAKE2s. For example, to replace SHA-1 with BLAKE2b without changing |
| 183 the size of output, we can tell BLAKE2b to produce 20-byte digests: |
| 184 |
| 185 >>> from hashlib import blake2b |
| 186 >>> h = blake2b(digest_size=20) |
| 187 >>> h.update(b'Replacing SHA1 with the more secure function') |
| 188 >>> h.hexdigest() |
| 189 'd24f26cf8de66472d58d4e1b1774b4c9158b1f4c' |
| 190 >>> h.digest_size |
| 191 20 |
| 192 >>> len(h.digest()) |
| 193 20 |
| 194 |
| 195 Hash objects with different digest sizes have completely different outputs |
| 196 (shorter hashes are *not* prefixes of longer hashes); BLAKE2b and BLAKE2s |
| 197 produce different outputs even if the output length is the same: |
| 198 |
| 199 >>> from hashlib import blake2b, blake2s |
| 200 >>> blake2b(digest_size=10).hexdigest() |
| 201 '6fa1d8fcfd719046d762' |
| 202 >>> blake2b(digest_size=11).hexdigest() |
| 203 'eb6ec15daf9546254f0809' |
| 204 >>> blake2s(digest_size=10).hexdigest() |
| 205 '1bf21a98c78a1c376ae9' |
| 206 >>> blake2s(digest_size=11).hexdigest() |
| 207 '567004bf96e4a25773ebf4' |
| 208 |
| 209 |
| 210 Keyed hashing |
| 211 ------------- |
| 212 |
| 213 Keyed hashing can be used for authentication as a faster and simpler |
| 214 replacement for `Hash-based message authentication code |
| 215 <http://en.wikipedia.org/wiki/Hash-based_message_authentication_code>`_ (HMAC). |
| 216 BLAKE2 can be securely used in prefix-MAC mode thanks to the |
| 217 indifferentiability property inherited from BLAKE. |
| 218 |
| 219 This example shows how to get a (hex-encoded) 128-bit authentication code for |
| 220 message ``b'message data'`` with key ``b'pseudorandom key'``: |
| 221 |
| 222 >>> from hashlib import blake2b |
| 223 >>> h = blake2b(key=b'pseudorandom key', digest_size=16) |
| 224 >>> h.update(b'message data') |
| 225 >>> h.hexdigest() |
| 226 '3d363ff7401e02026f4a4687d4863ced' |
| 227 |
| 228 |
| 229 As a practical example, a web application can symmetrically sign cookies sent |
| 230 to users and later verify them to make sure they weren't tampered with: |
| 231 |
| 232 >>> from hashlib import blake2b |
| 233 >>> from hmac import compare_digest |
| 234 >>> |
| 235 >>> SECRET_KEY = b'pseudorandomly generated server secret key' |
| 236 >>> AUTH_SIZE = 16 |
| 237 >>> |
| 238 >>> def sign(cookie): |
| 239 ... h = blake2b(data=cookie, digest_size=AUTH_SIZE, key=SECRET_KEY) |
| 240 ... return h.hexdigest() |
| 241 >>> |
| 242 >>> cookie = b'user:vatrogasac' |
| 243 >>> sig = sign(cookie) |
| 244 >>> print("{0},{1}".format(cookie.decode('utf-8'), sig)) |
| 245 user:vatrogasac,349cf904533767ed2d755279a8df84d0 |
| 246 >>> compare_digest(cookie, sig) |
| 247 True |
| 248 >>> compare_digest(b'user:policajac', sig) |
| 249 False |
| 250 >>> compare_digesty(cookie, '0102030405060708090a0b0c0d0e0f00') |
| 251 False |
| 252 |
| 253 Even though there's a native keyed hashing mode, BLAKE2 can, of course, be used |
| 254 in HMAC construction with :mod:`hmac` module: |
| 255 |
| 256 >>> import hmac, hashlib |
| 257 >>> m = hmac.new(b'secret key', digestmod=hashlib.blake2s) |
| 258 >>> m.update(b'message') |
| 259 >>> m.hexdigest() |
| 260 'e3c8102868d28b5ff85fc35dda07329970d1a01e273c37481326fe0c861c8142' |
| 261 |
| 262 |
| 263 Randomized hashing |
| 264 ------------------ |
| 265 |
| 266 By setting *salt* parameter users can introduce randomization to the hash |
| 267 function. Randomized hashing is useful for protecting against collision attacks |
| 268 on the hash function used in digital signatures. |
| 269 |
| 270 Randomized hashing is designed for situations where one party, the message |
| 271 preparer, generates all or part of a message to be signed by a second |
| 272 party, the message signer. If the message preparer is able to find |
| 273 cryptographic hash function collisions (i.e., two messages producing the |
| 274 same hash value), then she might prepare meaningful versions of the message |
| 275 that would produce the same hash value and digital signature, but with |
| 276 different results (e.g., transferring $1,000,000 to an account, rather than |
| 277 $10). Cryptographic hash functions have been designed with collision |
| 278 resistance as a major goal, but the current concentration on attacking |
| 279 cryptographic hash functions may result in a given cryptographic hash |
| 280 function providing less collision resistance than expected. Randomized |
| 281 hashing offers the signer additional protection by reducing the likelihood |
| 282 that a preparer can generate two or more messages that ultimately yield the |
| 283 same hash value during the digital signature generation process – even if |
| 284 it is practical to find collisions for the hash function. However, the use |
| 285 of randomized hashing may reduce the amount of security provided by a |
| 286 digital signature when all portions of the message are prepared |
| 287 by the signer. |
| 288 |
| 289 (`NIST SP-800-106 "Randomized Hashing for Digital Signatures" |
| 290 <http://csrc.nist.gov/publications/nistpubs/800-106/NIST-SP-800-106.pdf>`_) |
| 291 |
| 292 In BLAKE2 the salt is processed as a one-time input to the hash function during |
| 293 initialization, rather than as an input to each compression function. |
| 294 |
| 295 .. warning:: |
| 296 |
| 297 *Salted hashing* (or just hashing) with BLAKE2 or any other general-purpose |
| 298 cryptographic hash function, such as SHA-256, is not suitable for hashing |
| 299 passwords. See `BLAKE2 FAQ <https://blake2.net/#qa>`_ for more |
| 300 information. |
| 301 .. |
| 302 |
| 303 >>> import os |
| 304 >>> from hashlib import blake2b |
| 305 >>> msg = b'some message' |
| 306 >>> # Calculate the first hash with a random salt. |
| 307 >>> salt1 = os.urandom(blake2b.SALT_SIZE) |
| 308 >>> h1 = blake2b(salt=salt1) |
| 309 >>> h1.update(msg) |
| 310 >>> # Calculate the second hash with a different random salt. |
| 311 >>> salt2 = os.urandom(blake2b.SALT_SIZE) |
| 312 >>> h2 = blake2b(salt=salt2) |
| 313 >>> h2.update(msg) |
| 314 >>> # The digests are different. |
| 315 >>> h1.digest() != h2.digest() |
| 316 True |
| 317 |
| 318 |
| 319 Personalization |
| 320 --------------- |
| 321 |
| 322 Sometimes it is useful to force hash function to produce different digests for |
| 323 the same input for different purposes. Quoting the authors of the Skein hash |
| 324 function: |
| 325 |
| 326 We recommend that all application designers seriously consider doing this; |
| 327 we have seen many protocols where a hash that is computed in one part of |
| 328 the protocol can be used in an entirely different part because two hash |
| 329 computations were done on similar or related data, and the attacker can |
| 330 force the application to make the hash inputs the same. Personalizing each |
| 331 hash function used in the protocol summarily stops this type of attack. |
| 332 |
| 333 (`The Skein Hash Function Family |
| 334 <http://www.skein-hash.info/sites/default/files/skein1.3.pdf>`_, |
| 335 p. 21) |
| 336 |
| 337 BLAKE2 can be personalized by passing bytes to the *person* argument: |
| 338 |
| 339 >>> from hashlib import blake2b |
| 340 >>> FILES_HASH_PERSON = b'MyApp Files Hash' |
| 341 >>> BLOCK_HASH_PERSON = b'MyApp Block Hash' |
| 342 >>> h = blake2b(digest_size=32, person=FILES_HASH_PERSON) |
| 343 >>> h.update(b'the same content') |
| 344 >>> h.hexdigest() |
| 345 '20d9cd024d4fb086aae819a1432dd2466de12947831b75c5a30cf2676095d3b4' |
| 346 >>> h = blake2b(digest_size=32, person=BLOCK_HASH_PERSON) |
| 347 >>> h.update(b'the same content') |
| 348 >>> h.hexdigest() |
| 349 'cf68fb5761b9c44e7878bfb2c4c9aea52264a80b75005e65619778de59f383a3' |
| 350 |
| 351 Personalization together with the keyed mode can also be used to derive differen
t |
| 352 keys from a single one. |
| 353 |
| 354 >>> from hashlib import blake2s |
| 355 >>> from base64 import b64decode, b64encode |
| 356 >>> orig_key = b64decode(b'Rm5EPJai72qcK3RGBpW3vPNfZy5OZothY+kHY6h21KM=') |
| 357 >>> enc_key = blake2s(key=orig_key, person=b'kEncrypt').digest() |
| 358 >>> mac_key = blake2s(key=orig_key, person=b'kMAC').digest() |
| 359 >>> print(b64encode(enc_key).decode('utf-8')) |
| 360 rbPb15S/Z9t+agffno5wuhB77VbRi6F9Iv2qIxU7WHw= |
| 361 >>> print(b64encode(mac_key).decode('utf-8')) |
| 362 G9GtHFE1YluXY1zWPlYk1e/nWfu0WSEb0KRcjhDeP/o= |
| 363 |
| 364 Tree mode |
| 365 --------- |
| 366 |
| 367 Here's an example of hashing a minimal tree with two leaf nodes:: |
| 368 |
| 369 10 |
| 370 / \ |
| 371 00 01 |
| 372 |
| 373 The example uses 64-byte internal digests, and returns the 32-byte final |
| 374 digest. |
| 375 |
| 376 >>> from hashlib import blake2b |
| 377 >>> |
| 378 >>> FANOUT = 2 |
| 379 >>> DEPTH = 2 |
| 380 >>> LEAF_SIZE = 4096 |
| 381 >>> INNER_SIZE = 64 |
| 382 >>> |
| 383 >>> buf = bytearray(6000) |
| 384 >>> |
| 385 >>> # Left leaf |
| 386 ... h00 = blake2b(buf[0:LEAF_SIZE], fanout=FANOUT, depth=DEPTH, |
| 387 ... leaf_size=LEAF_SIZE, inner_size=INNER_SIZE, |
| 388 ... node_offset=0, node_depth=0, last_node=False) |
| 389 >>> # Right leaf |
| 390 ... h01 = blake2b(buf[LEAF_SIZE:], fanout=FANOUT, depth=DEPTH, |
| 391 ... leaf_size=LEAF_SIZE, inner_size=INNER_SIZE, |
| 392 ... node_offset=1, node_depth=0, last_node=True) |
| 393 >>> # Root node |
| 394 ... h10 = blake2b(digest_size=32, fanout=FANOUT, depth=DEPTH, |
| 395 ... leaf_size=LEAF_SIZE, inner_size=INNER_SIZE, |
| 396 ... node_offset=0, node_depth=1, last_node=True) |
| 397 >>> h10.update(h00.digest()) |
| 398 >>> h10.update(h01.digest()) |
| 399 >>> h10.hexdigest() |
| 400 '3ad2a9b37c6070e374c7a8c508fe20ca86b6ed54e286e93a0318e95e881db5aa' |
| 401 |
| 402 Credits |
| 403 ======= |
| 404 |
| 405 BLAKE2_ was designed by *Jean-Philippe Aumasson*, *Samuel Neves*, *Zooko |
| 406 Wilcox-O'Hearn*, and *Christian Winnerlein* based on SHA-3_ finalist BLAKE_ |
| 407 created by *Jean-Philippe Aumasson*, *Luca Henzen*, *Willi Meier*, and |
| 408 *Raphael C.-W. Phan*. |
| 409 |
| 410 It uses core algorithm from ChaCha_ cipher designed by *Daniel J. Bernstein*. |
| 411 |
| 412 The stdlib implementation is based on pyblake2_ module. It was written by |
| 413 *Dmitry Chestnykh* based on C implementation written by *Samuel Neves*. The |
| 414 documentation was copied from pyblake2_ and written by *Dmitry Chestnykh*. |
| 415 |
| 416 The C code was partly rewritten for Python by *Christian Heimes*. |
| 417 |
| 418 The following public domain dedication applies for both C hash function |
| 419 implementation, extension code, and this documentation: |
| 420 |
| 421 To the extent possible under law, the author(s) have dedicated all copyright |
| 422 and related and neighboring rights to this software to the public domain |
| 423 worldwide. This software is distributed without any warranty. |
| 424 |
| 425 You should have received a copy of the CC0 Public Domain Dedication along |
| 426 with this software. If not, see |
| 427 http://creativecommons.org/publicdomain/zero/1.0/. |
| 428 |
| 429 The following people have helped with development or contributed their changes |
| 430 to the project and the public domain according to the Creative Commons Public |
| 431 Domain Dedication 1.0 Universal: |
| 432 |
| 433 * *Alexandr Sokolovskiy* |
| 434 |
| 435 .. seealso:: Official BLAKE2 website: https://blake2.net |
| 436 |
| 437 .. _BLAKE2: https://blake2.net |
| 438 .. _HMAC: http://en.wikipedia.org/wiki/Hash-based_message_authentication_code |
| 439 .. _BLAKE: https://131002.net/blake/ |
| 440 .. _SHA-3: http://en.wikipedia.org/wiki/NIST_hash_function_competition |
| 441 .. _ChaCha: http://cr.yp.to/chacha.html |
| 442 .. _pyblake2: https://pythonhosted.org/pyblake2/ |
| 443 |
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