How to encrypt Epub?

[icearch]

How to encrypt Epub so others can't change it's comtent? Is this even possible?

[Doitsu]

Originally Posted by icearch

How to encrypt Epub so others can't change it's comtent? Is this even possible?

Can't be done, unless you write your own app. See also How to make an EPUB file read-only/non-modifiable?

[icearch]

Well how does pdf achieve this? Pdf can be set to read-only (require password to edit) or require password to read. But it seems fine to read on any other apps that supports pdf.
Is it because encryption is not a thing in mind when creating epub standards?

[JSWolf]

Originally Posted by icearch

How to encrypt Epub so others can't change it's comtent? Is this even possible?

Apple's current DRM has not been broken. You could sell your ePub through Apple.

[QuietShelfLife]

The short answer is that PDF has password protection baked into the format spec — every PDF reader knows how to handle it. EPUB is basically a zip of HTML files, so there's nothing like that built in. You'd need an external DRM system (Readium LCP, Apple FairPlay, Adobe ADEPT) and those all require certified reader apps to work. It's a fundamental design difference between the two formats.

[Jellby]

You can password-protect a zip, and therefore also an epub. It would probably no longer be a spec-compliant epub and few applications (if any) would recognize and open it as an epub.

But before you embark into creating or modifying an app to read those files, note that anyone with the password to open the book and read it would also have the password to open the book and modify it.

If your concern is not so much preventing modification, but being able to tell whether the book is the original or a modified copy, you can always publish some checksum like md5 or sha-256. That way your readers could verify that their copy is identical to the one approved by you.

[icearch]

Originally Posted by Jellby

You can password-protect a zip, and therefore also an epub. It would probably no longer be a spec-compliant epub and few applications (if any) would recognize and open it as an epub.

But before you embark into creating or modifying an app to read those files, note that anyone with the password to open the book and read it would also have the password to open the book and modify it.

If your concern is not so much preventing modification, but being able to tell whether the book is the original or a modified copy, you can always publish some checksum like md5 or sha-256. That way your readers could verify that their copy is identical to the one approved by you.

That's good! I will look into md5 and such.

[icearch]

Originally Posted by QuietShelfLife

The short answer is that PDF has password protection baked into the format spec — every PDF reader knows how to handle it. EPUB is basically a zip of HTML files, so there's nothing like that built in. You'd need an external DRM system (Readium LCP, Apple FairPlay, Adobe ADEPT) and those all require certified reader apps to work. It's a fundamental design difference between the two formats.

I see, thx.

[Doitsu]

Originally Posted by Jellby

If your concern is not so much preventing modification, but being able to tell whether the book is the original or a modified copy, you can always publish some checksum like md5 or sha-256. That way your readers could verify that their copy is identical to the one approved by you.

Theoretically, the OP could add a signatures.xml file to the META-INF folder of epub3 books. But they'd have to provide their own custom validation tool.

Moreover, the W3C stated:

Adding a digital signature is not a guarantee that a malicious actor cannot tamper with an EPUB publication as reading systems do not have to check signatures.

(emphasis mine)

[Quoth]

Originally Posted by icearch

Well how does pdf achieve this? Pdf can be set to read-only (require password to edit) or require password to read. But it seems fine to read on any other apps that supports pdf.
Is it because encryption is not a thing in mind when creating epub standards?

PDF only partially achieves this and isn't reflow-able and can covert to image only.

If people can see it, then ultimately any DRM can be defeated.