1 files changed, 46 insertions, 0 deletions
diff --git a/share/certs/PrivateKeyNotes.md b/share/certs/PrivateKeyNotes.md
new file mode 100644
index 0000000000..da299d168f
--- /dev/null
+++ b/share/certs/PrivateKeyNotes.md
@@ -0,0 +1,46 @@
+Code-signing private key notes
+==
+
+The private keys for these certificates were generated on Gavin's main work machine,
+following the certificate authoritys' recommendations for generating certificate
+signing requests.
+
+For OSX, the private key was generated by Keychain.app on Gavin's main work machine.
+The key and certificate is in a separate, passphrase-protected keychain file that is
+unlocked to sign the Bitcoin-Qt.app bundle.
+
+For Windows, the private key was generated by Firefox running on Gavin's main work machine.
+The key and certificate were exported into a separate, passphrase-protected PKCS#12 file, and
+then deleted from Firefox's keystore. The exported file is used to sign the Windows setup.exe.
+
+Threat analysis
+--
+
+Gavin is a single point of failure. He could be coerced to divulge the secret signing keys,
+allowing somebody to distribute a Bitcoin-Qt.app or bitcoin-qt-setup.exe with a valid
+signature but containing a malicious binary.
+
+Or the machine Gavin uses to sign the binaries could be compromised, either remotely or
+by breaking in to his office, allowing the attacker to get the private key files and then
+install a keylogger to get the passphrase that protects them.
+
+Threat Mitigation
+--
+
+"Air gapping" the machine used to do the signing will not work, because the signing
+process needs to access a timestamp server over the network. And it would not
+prevent the "rubber hose cryptography" threat (coercing Gavin to sign a bad binary
+or divulge the private keys).
+
+Windows binaries are reproducibly 'gitian-built', and the setup.exe file created
+by the NSIS installer system is a 7zip archive, so you could check to make sure
+that the bitcoin-qt.exe file inside the installer had not been tampered with.
+However, an attacker could modify the installer's code, so when the setup.exe
+was run it compromised users' systems. A volunteer to write an auditing tool
+that checks the setup.exe for tampering, and checks the files in it against
+the list of gitian signatures, is needed.
+
+The long-term solution is something like the 'gitian downloader' system, which
+uses signatures from multiple developers to determine whether or not a binary
+should be trusted. However, that just pushes the problem to "how will
+non-technical users securely get the gitian downloader code to start?"