Hey all! Love Cybrary and I’m going through the Security+ videos now. I have a question that isn’t really relevant to Security+, it’s just something I’m curious about. In video 1.12, the speaker mentions that asymmetric crypto involves someone having a public key and a private key, and it works via the owner handing out his public key to anyone who wants it. Thus, a recipient can use that public key to encrypt a message and send it to the owner, who is the only one who can decrypt it (via his private key).
Question: If the public key is publicly available, and it instructs a user’s app on how to encrypt a message (so it will be decryptable by the owner), then can’t anyone just analyze the public key to see how it encrypts, and thus decrypt any message?
Hey there! I’m sure someone else can provide a more satisfying technical explanation of why a public key can’t be used to infer the private key, but the short answer is that the public key is derived from the private key using a one-way cryptographic function.
This means that calculating the private key from the public key, though technically possible, is inordinately difficult, requiring significant computing power, and highly impractical within reasonable timeframes.
TLDR yes it is a solvable math problem, but it’s not a math problem you want to try to solve - unless you’re very determined and well-resourced.