2018-05-15 03:13:16 +00:00
|
|
|
<?xml version="1.0" encoding="UTF-8"?>
|
|
|
|
|
<!DOCTYPE dita PUBLIC "-//OASIS//DTD DITA Composite//EN" "ditabase.dtd">
|
2018-05-15 03:50:14 +00:00
|
|
|
<dita xml:lang="en-GB">
|
2018-05-15 03:13:16 +00:00
|
|
|
<topic id="topic_vqx_tqy_5db">
|
|
|
|
|
<title>Decryption</title>
|
|
|
|
|
<body>
|
|
|
|
|
<p>Decrypting something encrypted to a key in one's secret keyring is fairly straight
|
|
|
|
|
forward.</p>
|
|
|
|
|
<p>In this example code, however, preconfiguring either <codeph>gpg.Context()</codeph> or
|
|
|
|
|
<codeph>gpg.core.Context()</codeph> as <codeph>c</codeph> is unnecessary because there is
|
|
|
|
|
no need to modify the Context prior to conducting the decryption and since the Context is
|
|
|
|
|
only used once, setting it to c simply adds lines for no gain.</p>
|
|
|
|
|
<p>
|
|
|
|
|
<codeblock id="decry-1" outputclass="language-python">import gpg
|
|
|
|
|
|
|
|
|
|
ciphertext = input("Enter path and filename of encrypted file: ")
|
|
|
|
|
newfile = input("Enter path and filename of file to save decrypted data to: ")
|
|
|
|
|
|
|
|
|
|
with open(ciphertext, "rb") as cfile:
|
2018-05-23 05:08:03 +00:00
|
|
|
try:
|
|
|
|
|
plaintext, result, verify_result = gpg.Context().decrypt(cfile)
|
|
|
|
|
except gpg.errors.GPGMEError as e:
|
|
|
|
|
plaintext = None
|
|
|
|
|
print(e)
|
2018-05-15 03:13:16 +00:00
|
|
|
|
2018-05-23 05:08:03 +00:00
|
|
|
if plaintext is not None:
|
|
|
|
|
with open(newfile, "wb") as nfile:
|
|
|
|
|
nfile.write(plaintext)
|
|
|
|
|
else:
|
|
|
|
|
pass
|
2018-05-15 03:13:16 +00:00
|
|
|
</codeblock>
|
|
|
|
|
</p>
|
2018-06-28 08:02:43 +00:00
|
|
|
<p>The data available in <codeph>plaintext</codeph> following a successful decryption in this
|
|
|
|
|
example is the decrypted content as a byte object, the recipient key IDs and algorithms in
|
|
|
|
|
<codeph>result</codeph> and the results of verifying any signatures of the data in
|
|
|
|
|
<codeph>verify_result</codeph>.</p>
|
|
|
|
|
<p>
|
|
|
|
|
<note>The graceful handling of <codeph>GPGMEError</codeph> with the try/except statement is
|
|
|
|
|
to handle the decryption error message produced if the file <codeph>ciphertext</codeph>,
|
|
|
|
|
and thus <codeph>cfile</codeph>, are encrypted with deprecated and insecure methods.
|
|
|
|
|
Particularly without MDC integrity checks or utilising deprecated encryption algorithms.
|
|
|
|
|
Messages and files encrypted with these are not decrypted with GPGME at all and any user
|
|
|
|
|
requiring archival access will need to access it manually with pre-GnuPG 2.3 versions of
|
|
|
|
|
the software which meets the requirements of the specific use case.</note>
|
|
|
|
|
</p>
|
|
|
|
|
<p/>
|
2018-05-15 03:13:16 +00:00
|
|
|
</body>
|
|
|
|
|
</topic>
|
|
|
|
|
</dita>
|
