If I have a passphrase-protected SSH private key,
if this passphrase is sufficiently random and long (say, 20-, 30-, 40-characters long, or even more!),
if I make this private key of mine publicly available on the Net
will it be practically possible for someone to be able to decrypt my private key from its corresponding public key (the latter being publicly available anyway).
My guess the answer is most likely going to be:
"The decryption effort and time taken will be totally dependent on the length and randomness of the passphrase chosen, and there is nothing inherent in SSH authentication algorithms/protocols that would speed up or slow down the decryption effort. Thus, in the current state-of-decryption-art, a 20+ characters long passphrase should be sufficient enough. Even Gmail et al are recommending passphrases much smaller in length."
But I'm not sure if this is the right answer, or if there are any other aspects to it that I need to worry about, etc.
If this SSH private key is really not practically decryptable, then I intend to protect it with a VERY long passphrase and then forget all about securing the key itself. I, for example, could store it in my Gmail inbox (letting even Gmail team see it), or even upload it on my personal website for my easy retrieval (say, when I'm travelling). Etc.