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diff --git a/src/content/blogs/the-search-for-the-perfect-ssh-key.mdx b/src/content/blogs/the-search-for-the-perfect-ssh-key.mdx deleted file mode 100644 index 09cc13c..0000000 --- a/src/content/blogs/the-search-for-the-perfect-ssh-key.mdx +++ /dev/null @@ -1,117 +0,0 @@ ---- -title: The search for the perfect SSH key -description: How you can embed your name in an SSH key -date: 2024-11-15 ---- - -SSH keys are a widely used tool among developers, -they are the equivalent of a username and password in the development world. -They allow you to prove your identity and they are the gateway -into accessing servers remotely in a secure manner. - -## The SSH public key format - -When generating an ssh key, you get 2 files, one with no extension that stores the private key -and another that ends with a `.pub`. -The public key is what you share publicly on your profile or add to a remote server to login through SSH. - -Here's how a typical SSH public key looks - -``` -ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIBSSj+yfJLWEb+Df4r4603TOFAUBREYS43qQB+c9i9UW -``` - -It consists of 2 parts, the algorithm, in this case it's -`ssh-ed25519`, but it can be other ones too such as `ssh-rsa`. -The second part is a base64 encoded custom binary format. - -Let's break it down - -- the length of the algorithm string, for ed25519 it's always 11 (4 bytes long) -- the algorithm type, for ed25519 it's always `ssh-ed25519` in binary (11 bytes long) -- the length of the key, 32 bytes for ed25519 (4 bytes long) -- the raw bytes for the ed25519 key (32 bytes long) - -## Embedding a word in base64 - -Base64 is a widely used format for displaying binary in a compact and human readable way, -it uses A-Z, a-z, 0-9, '/' and '+' adding up to 64 unique characters. - -It's possible to choose specific bytes in a way that when encoding it with base64 -it will form a word. - -For example, to encode "Kyren" in base64, we can use the bytes -`00101011 00101010 01001110` or in hex `2b 2a de`. - -So by controlling the 32 bytes at the end of the ssh we are able to get -a ssh public key containig any keyword we want. - -## Brute Force - -Unfortunately this approach won't work, we still want to be able to use the key -so we will need to know the corresponding private key, but it's impossible to reverse engineer -the private key using the public one, that's why cryptography is so secure. - -The solution is simple, just generate a bunch of keys until we get lucky and find the desired keyword. -So that's what I have done, here's a basic go program that does exactly that. - -```go -package main - -import ( - "bytes" - "crypto/ed25519" - "encoding/base64" - "fmt" - - "golang.org/x/crypto/ssh" -) - -func main() { - keyword := []byte("Kyren") - for { - pubKey, privKey, _ := ed25519.GenerateKey(nil) - sshPubKey, _ := ssh.NewPublicKey(pubKey) - pub := ssh.MarshalAuthorizedKey(sshPubKey) - if bytes.Contains(pub, keyword) { - privBase64 := base64.StdEncoding.EncodeToString(privKey) - fmt.Printf("Found %s in %s with private key %s\n", string(keyword), string(pub), privBase64) - break - } - } -} -``` - -I have later improved this program by adding multithreading and made it easier to use. -The final code is available on my GitHub [at this link](https://github.com/Kyren223/ed25519-key-gen). - -## Results - -After running it for 2 days (about 24 hours in total) on my AMD Ryzen 5 7530U laptop (12 threads), -here are the results: - -``` -Completed Search -Time Elapsed: 12h9m11.225248108s -Searched: 6733606724 Found: 737 -``` - -- Generated and searched 150k SSH keys per second -- Found a 5-character keyword every 9.1 million keys or about 1 every minute -- Found a 6 character keyword every 1/64 of every 5-character keyword, or about 1 every hour -- Found 5-character that are at the end of the SSH key 1/50 of every 5-character keyword - -My goal was to find a `/kyren` at the end of the key, -on average that'd be 1 every 3200 5-character keywords. - -At the end after only 1862 keywords I found the key, here it is - -``` -ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIO7P9K9D5RkBk+JCRRS6AtHuTAc6cRpXfRfRMg/Kyren -``` - -I hope this inspires you to try and find your own SSH key, -hopefully your name is not 7 characters long, -and if it's 8, I hope you have 170 years to spare. - -Thanks for reading! this is my first blog post so any feedback will be appreciated! |