So, to calculate the PKCE code challenge, you need to use a SHA256 function that can give you the raw bytes, then use a modified Base64 encoding function to encode those bytes. This makes it URL-safe, since otherwise the +/= characters would need to be escaped in the URL. Base64-URL-encoding is a minor variation of Base64 encoding, where the only difference is using the character - instead of + and _ instead of /, and trimming the = padding characters from the end. The next problem is that you need to base64-url encode, not base64 encode. You need to use a hash function that outputs the raw bytes, and pass the raw bytes into the base64-url-encoder. So the next thing you're doing by base64 encoding is that you're base64 encoding the hex representation of the hash rather than the raw bytes. That's typically helpful, but in this case is not. The online SHA256 hash calculator you found outputs the hash as a hex-encoded string rather than the raw bytes. There are two problems with what you've tried to do above: That's a lot of words, so let's walk through it. This means you need to take the original string, calculate the SHA256 hash of it, then Base64-URL-encode the hash. The PKCE code challenge is the Base64-URL-encoded SHA256 hash of the verifier. What am I doing that's causing this discrepancy? How do I calculate the expected code_verifier value of iF_7prUeJ6rr3jMG3LmhW3R1cZ2ecZavFqS0jtb6tzo? Thanks At the rate Bitcoin is going, it would take them. Lets say you were trying to perform a collision attack and would 'only' need to calculate 2128 2 128 hashes. Using this calculator I get iF/7prUeJ6rr3jMG3LmhW3R1cZ2ecZavFqS0jtb6tzo which is one character off from the expected value (notice how there's a / instead of _). For comparison, as of January 2015, Bitcoin was computing 300 quadrillion SHA-256 hashes per second. This SHA256 base 64 hash calculator from approsto gives me a value that is very close to the expected value. What am I doing wrong to not get the expected value? Using this SHA256 hash calculator and Base64 Encoder, I got ODg1ZmZiYTZiNTFlMjdhYWViZGUzMzA2ZGNiOWExNWI3NDc1NzE5ZDllNzE5NmFmMTZhNGI0OGVkNmZhYjczYQ which doesn't match the expected value of iF_7prUeJ6rr3jMG3LmhW3R1cZ2ecZavFqS0jtb6tzo. IF_7prUeJ6rr3jMG3LmhW3R1cZ2ecZavFqS0jtb6tzo as the code challenge? Using Zg6klgrnixQJ629GsawRMV8MjWvwRAr-vyvP1MHnB6X8WKZN as the code verifier, how did they produce This script was developed for use in EnCase training.I'm going through Okta's PCKE Flow demo to get a better understanding of how it works, and I'm having trouble reproducing the same code_challenge hash that's being generated from the code_verifier. The 'Send Process Hash to VirusTotal' option does not work with the Analysis Browser, which is an EnScript shown in the EnCase GUI. Note that for this option to work, the list of processes must be promoted to the table pane using the Browse Data button. Q: What is sha256 hash A: Please read the document. The script will use the SHA-1 hash if available. You can generate hash in different formats like binary, hex, base64 etc. The 'Send Process Hash to VirusTotal' option can be used to send a snapshot process-hash to VirusTotal. Note that this is a 'cheap' way of performing lookups that may, on occasion, cause the VirusTotal website to present a Captcha dialog or block access in an effort to prevent abuse of service. Taking the 'Send SHA-256 Hash to VirusTotal' option will cause the script to open a URL taking the user's default browser to VirusTotal so that he/she can view the analysis results for the hash in question. The script will present the calculated hash-values in a dialog box it will also write them to the console window. The script can also hash the highlighted ANSI/ASCII text with the option of editing that text beforehand. Otherwise it will hash the item's entire logical content. If the second option is chosen the script will hash the data highlighted by the user provided that something other than just the first byte at the start of the item's data has been selected. The script can hash the item's entire logical content or it can determine what to hash automatically based on the user's selection. The script will also calculate a version of the MD-4 hash used by the eMule & eDonkey file-sharing software. This plug-in calculates ADLER, CRC-32, MD-4, MD-5, SHA-1, SHA-256 and SHA-512 hash-values for the highlighted item.
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