[catapult] - Copy Telemetry's gsutilz over to third_party.

third_party/gsutil/third_party/rsa/doc/compatibility.rst

Index: third_party/gsutil/third_party/rsa/doc/compatibility.rst
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+Compatibility with standards
+==================================================
+
+.. index:: OpenSSL
+.. index:: compatibility
+
+Python-RSA implements encryption and signatures according to PKCS#1
+version 1.5. This makes it compatible with the OpenSSL RSA module.
+
+Keys are stored in PEM or DER format according to PKCS#1 v1.5. Private
+keys are compatible with OpenSSL. However, OpenSSL uses X.509 for its
+public keys, which are not supported.
+
+Encryption:
+    PKCS#1 v1.5 with at least 8 bytes of random padding
+
+Signatures:
+    PKCS#1 v1.5 using the following hash methods:
+    MD5, SHA-1, SHA-256, SHA-384, SHA-512
+
+Private keys:
+    PKCS#1 v1.5 in PEM and DER format, ASN.1 type RSAPrivateKey
+
+Public keys:
+    PKCS#1 v1.5 in PEM and DER format, ASN.1 type RSAPublicKey
+
+:ref:`VARBLOCK <bigfiles>` encryption:
+    Python-RSA only, not compatible with any other known application.
+
+.. _openssl:
+
+Interoperability with OpenSSL
+--------------------------------------------------
+
+You can create a 512-bit RSA key in OpenSSL as follows::
+
+    openssl genrsa -out myprivatekey.pem 512
+
+To get a Python-RSA-compatible public key from OpenSSL, you need the
+private key first, then run it through the ``pyrsa-priv2pub``
+command::
+
+    pyrsa-priv2pub -i myprivatekey.pem -o mypublickey.pem
+
+Encryption and decryption is also compatible::
+
+    $ echo hello there > testfile.txt
+    $ pyrsa-encrypt -i testfile.txt -o testfile.rsa publickey.pem
+    $ openssl rsautl -in testfile.rsa -inkey privatekey.pem -decrypt
+    hello there
+
+Interoperability with PKCS#8
+--------------------------------------------------
+
+The standard PKCS#8 is widely used, and more complex than the PKCS#1
+v1.5 supported by Python-RSA. In order to extract a key from the
+PKCS#8 format you need an external tool such as OpenSSL::
+
+    openssl rsa -in privatekey-pkcs8.pem -out privatekey.pem
+
+You can then extract the corresponding public key as described above.
+