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Error in Decryption Test (youtube_genalgo.py) #1099

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opened 2026-02-20 23:20:29 -05:00 by deekerman · 6 comments

deekerman commented

2026-02-20 23:20:29 -05:00

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Originally created by @JamesRickman4 on GitHub (Sep 16, 2013).

I think there is an error in the line...

tests = [
#92 - vflQw-fB4 2013/07/17
("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&()-+={[]}|:;?/>.<'`~"",
"mrtyuioplkjhgfdsazxcvbnq1234567890QWERTY}IOPLKJHGFDSAZXCVBNM!@#$%^&()-+={[]"|:;"),

The input test string is actually 93 characters if you count them and I don't think you wanted to include quotes as a test character in the string like you did at the end of the input string (the test has "" at the end).

I am interested in how you derive the algorithms to decrypt the signature. Are those published somewhere?

Thanks,
James

Originally created by @JamesRickman4 on GitHub (Sep 16, 2013). I think there is an error in the line... tests = [ #92 - vflQw-fB4 2013/07/17 ("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&_()_-+={[]}|:;?/>.<'`~\"", "mrtyuioplkjhgfdsazxcvbnq1234567890QWERTY}IOPLKJHGFDSAZXCVBNM!@#$%^&_()_-+={[]\"|:;"), The input test string is actually 93 characters if you count them and I don't think you wanted to include quotes as a test character in the string like you did at the end of the input string (the test has "" at the end). I am interested in how you derive the algorithms to decrypt the signature. Are those published somewhere? Thanks, James

deekerman closed this issue

2026-02-20 23:20:32 -05:00

deekerman commented

2026-02-20 23:20:33 -05:00

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@phihag commented on GitHub (Sep 16, 2013):

You're mistaken; the input string is 92 characters:

>>> len("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_-+={[]}|:;?/>.<'`~\"")
92

The signatures come from the HTML5 player code. I'm working on adding automated extraction. It works fine for HTML5, but alas is not finished for the Flash player.

@phihag commented on GitHub (Sep 16, 2013): You're mistaken; the input string _is_ 92 characters: ``` >>> len("qwertyuioplkjhgfdsazxcvbnm1234567890QWERTYUIOPLKJHGFDSAZXCVBNM!@#$%^&*()_-+={[]}|:;?/>.<'`~\"") 92 ``` The signatures come from the HTML5 player code. I'm working on adding automated extraction. It works fine for HTML5, but alas is not finished for the Flash player.

deekerman commented

2026-02-20 23:20:33 -05:00

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@JamesRickman4 commented on GitHub (Sep 16, 2013):

LOL...Interesting. But I think not. Looks like your Len function is lying to you. Try physically counting the characters. I assume we're talking from the 'q' character to the quote character (leaving off the first quote and the last quote....and that means the last character inside the quotes is a quote character). There are 93 characters.

Anyway, do your really want to use the quote character as a test character? I would think this would cause issues like this.

Thanks,
James

@JamesRickman4 commented on GitHub (Sep 16, 2013): LOL...Interesting. But I think not. Looks like your Len function is lying to you. Try physically counting the characters. I assume we're talking from the 'q' character to the quote character (leaving off the first quote and the last quote....and that means the last character inside the quotes is a quote character). There are 93 characters. Anyway, do your really want to use the quote character as a test character? I would think this would cause issues like this. Thanks, James

deekerman commented

2026-02-20 23:20:33 -05:00

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@Nothing4You commented on GitHub (Sep 16, 2013):

\" is a single character... it means a " which is escaped because it's inside a quoted string with " as delimiter

@Nothing4You commented on GitHub (Sep 16, 2013): `\"` is a single character... it means a `"` which is escaped because it's inside a quoted string with `"` as delimiter

deekerman commented

2026-02-20 23:20:33 -05:00

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@JamesRickman4 commented on GitHub (Sep 17, 2013):

Thanks for the insight. I don't know python syntax but I know how to count and the count added up to 93. But it seems my ignorance in python makes me wrong in the end. LOL Is there a reason for the test cast to go out of its way to use a character that you have to escape with the ""? Just curious now.

On a related note, I didn't fully understand phihag's comment above about the signatures coming from the HTML5 player code. Is that the video.js player or is he talking about something else? I ran across some interesting code from the youtube5 project that had a more formula based approach to the decryption algorithm. However, I could not get it to match the test cases results from the youtube-dl project. The code is below. Are you aware of the youtube5 approach? What is your take on it? I am looking for an algorithm description document (ADD) on how to decrypt the youtube URL download signatures. If you have any insight on that process I'm all ears.

self.signatureDecipher = {
    timestamp: 15902,

    clone: function(a, b) {
        return (a.slice(b));
    },

    decipher: function(s) {
        var t = s.split("");
        t = this.clone(t, 2);
        t = this.reverse(t);
        t = this.clone(t, 3);
        t = this.swap(t, 9);
        t = this.clone(t, 3);
        t = this.swap(t, 43);
        t = this.clone(t, 3);
        t = this.reverse(t);
        t = this.swap(t, 23);
        return (t.join(""));
    },

    swap: function(a, b) {
        var t1 = a[0];
        var t2 = a[(b % a.length)];
        a[0] = t2;
        a[b] = t1;
        return (a);
    },

    reverse: function(a) {
        a.reverse();
        return (a);
    }
};

Thanks,
James

@JamesRickman4 commented on GitHub (Sep 17, 2013): Thanks for the insight. I don't know python syntax but I know how to count and the count added up to 93. But it seems my ignorance in python makes me wrong in the end. LOL Is there a reason for the test cast to go out of its way to use a character that you have to escape with the "\"? Just curious now. On a related note, I didn't fully understand phihag's comment above about the signatures coming from the HTML5 player code. Is that the video.js player or is he talking about something else? I ran across some interesting code from the youtube5 project that had a more formula based approach to the decryption algorithm. However, I could not get it to match the test cases results from the youtube-dl project. The code is below. Are you aware of the youtube5 approach? What is your take on it? I am looking for an algorithm description document (ADD) on how to decrypt the youtube URL download signatures. If you have any insight on that process I'm all ears. ``` self.signatureDecipher = { timestamp: 15902, clone: function(a, b) { return (a.slice(b)); }, decipher: function(s) { var t = s.split(""); t = this.clone(t, 2); t = this.reverse(t); t = this.clone(t, 3); t = this.swap(t, 9); t = this.clone(t, 3); t = this.swap(t, 43); t = this.clone(t, 3); t = this.reverse(t); t = this.swap(t, 23); return (t.join("")); }, swap: function(a, b) { var t1 = a[0]; var t2 = a[(b % a.length)]; a[0] = t2; a[b] = t1; return (a); }, reverse: function(a) { a.reverse(); return (a); } }; ``` Thanks, James

deekerman commented

2026-02-20 23:20:34 -05:00

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@phihag commented on GitHub (Sep 17, 2013):

@JamesRickman4 This code is equivalent to one of the lines in our code that look like

return s[5:34] + s[0] + s[35:38] + s[3] + s[39:45] + s[38] + s[46:53] + s[73] + s[54:73] + s[85] + s[74:85] + s[53]

Please bear in mind that this is an issue tracker about issues with youtube-dl. If your copy of youtube-dl doesn't work in some way or you want to suggest an improvement, feel free to do so.

@phihag commented on GitHub (Sep 17, 2013): @JamesRickman4 This code is equivalent to one of the lines in our code that look like ``` return s[5:34] + s[0] + s[35:38] + s[3] + s[39:45] + s[38] + s[46:53] + s[73] + s[54:73] + s[85] + s[74:85] + s[53] ``` Please bear in mind that this is an issue tracker about issues with youtube-dl. If your copy of youtube-dl doesn't work in some way or you want to suggest an improvement, feel free to do so.

deekerman commented

2026-02-20 23:20:34 -05:00

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@JamesRickman4 commented on GitHub (Sep 17, 2013):

Ok. Fair enough. Thanks for the quick replies. I'll look elsewhere for answers to my questions. :-)

@JamesRickman4 commented on GitHub (Sep 17, 2013): Ok. Fair enough. Thanks for the quick replies. I'll look elsewhere for answers to my questions. :-)

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