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Corrected basic example

pull/82/head
David Nuñez 2018-02-26 16:02:31 +01:00
parent 560e986c44
commit 5ea439a1b1
1 changed files with 24 additions and 33 deletions

57
docs/source/using_pyumbral.rst
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@ -70,11 +70,11 @@ Threshold split-key re-encryption
==================================
Alice generates kfrags for Bob
-------------------------------
When Alice wants to send a re-encrypted message to Bob,
*threshold split re-encryption keys*, or *"kfrags"*, are created for
distribution and later reconstruction via "Shamir's Secret Sharing".
Alice grants access to Bob by generating kfrags
-----------------------------------------------
When Alice wants to grant Bob access to open her encrypted messages,
she creates *threshold split re-encryption keys*, or *"kfrags"*,
which are next sent to N proxies or *Ursulas*.
| Generate re-encryption key fragments with "`M` of `N`":
| `M` - Minimum threshold of key fragments needed to activate a capsule.
@ -107,7 +107,7 @@ S3, IPFS, Google Cloud, Sneakernet, etc.
Bob fails to open the capsule
-------------------------------
If Bob attempts to open a capsule that was not encrypted for his public key,
or re-encrypted for him by Ursula, He will not be able to open it.
or re-encrypted for him by Ursula, he will not be able to open it.
.. code-block:: python
@ -120,44 +120,35 @@ or re-encrypted for him by Ursula, He will not be able to open it.
print("Decryption failed!")
Bob gathers kfrags
-------------------
After alice generates (and distributes) re-encryption keys,
Bob must gather at least `M` `kfrags` in order to activate the capsule.
Let's mock a network or transport layer by sampling `M` random `kfrags`.
.. code-block:: python
import random
kfrags = random.sample(kfrags, # All kfrags from above
10) # M - Threshold
Ursula performs re-encryption
Ursulas perform re-encryption
------------------------------
After Bob gathers at least `M` re-encryption keys,
He presents them to *Ursula*, a proxy re-encryption actor.
Bob asks several Ursulas to re-encrypt the capsule so he can open it.
Each Ursula performs re-encryption on the capsule using the `kfrag`
provided by Alice, obtaining this way a "capsule fragment", or `cfrag`,
Let's mock a network or transport layer by sampling `M` random `kfrags`,
one for each required Ursula.
Ursula exchanges Bob's `kfrags` for "capsule fragments", or `cfrags`,
performing re-encryption with the capsule.
Bob collects the resulting `cfrags` from several Ursulas.
Bob must gather at least `M` `cfrags` in order to activate the capsule.
Bob collects the resulting `cfrags` from Ursula.
.. code-block:: python
cfrags = list() # Bob's cfrag collection
for kfrag in kfrags:
cfrag = umbral.reencrypt(kfrag, capsule)
cfrags.append(cfrag) # Bob collects a cfrag
import random
kfrags = random.sample(kfrags, # All kfrags from above
10) # M - Threshold
cfrags = list() # Bob's cfrag collection
for kfrag in kfrags:
cfrag = umbral.reencrypt(kfrag, capsule)
cfrags.append(cfrag) # Bob collects a cfrag
Bob attaches cfrags to the capsule
----------------------------------
Bob attaches at least `M` `cfrags` to the capsule;
Then it can then become *activated*.
Then it can become *activated*.
.. code-block:: python