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SSL/TLS best practices for websites
Keeping Secrets
SSL and its successor TLS are a never-ending source of surprises – even for me, and I have been using these encryption technologies since the early days of Netscape Navigator. When you think you finally understand SSL, a new mystery opens up, and you find yourself delving the depths again.
Most admins don't have time for long searches. Admins want to set up a secure HTTPS website as quickly as possible and turn to the next task. This article provides advice on using SSL for web practitioners, and I'll even include some sample files for Apache and Nginx.
1. Algorithms and Key Lengths
Currently, TLS supports three key algorithms: DSA is dead; the future belongs to elliptic curve cryptography with ECDSA, but older clients do not support it, so the standard also supports RSA for now.
The key length of 2048 bits for RSA keys, or 256 bits for ECDSA, should be sufficient for most purposes. Keys of this length offer 112 or 128 bits of encryption strength. If you want a future-proof solution, you can opt for a 3072-bit RSA key, which also gives you 128 bits of encryption.
2. KeyManagement
What is more important than the length of the key in practice, however, is the way the admin handles the keys. Much evidence suggests that the most successful attacks on SSL have not actually cracked the encryption but simply avoided it. If you can break into a server to steal the private keys, or otherwise gain access to them, you do not need to break your teeth on the cryptography.
The private keys must remain secret. Only a small group of employees should have access to these valuable files – just enough to ensure smooth operations.
Additionally, the admin should protect the keys with a password and enter a passphrase when generating them. These precautions reduce the risk if a backup of the system gets into the wrong
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