What's the most secure way to encrypt a PDF?

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davebo
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What's the most secure way to encrypt a PDF?

Post by davebo » Tue Sep 03, 2019 11:27 am

I know you can do it within Adobe, but I read somewhere that is the least effective way because (from what I remember) there are programs that easily crack any Adobe PDF. I understand that anything can probably be cracked with effort, but the jist I got was that it was just above minimal effort to crack.

Anything else? If not, I'll just use Adobe and hope for the best.

Thanks,

MotoTrojan
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Re: What's the most secure way to encrypt a PDF?

Post by MotoTrojan » Tue Sep 03, 2019 11:29 am

If this is for e-mail or other means of electronic file transfer you can encrypt using various .zip systems. I can't recall which I've used but it has 3 different security levels and the higher two are supposedly pretty solid. This is less convenient if you want it perpetually encrypted on your/someones PC since ones it is unzipped it will be totally unprotected on the recipients PC.

texasdiver
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Re: What's the most secure way to encrypt a PDF?

Post by texasdiver » Tue Sep 03, 2019 11:37 am

I know that when the government releases .pdf documents with redactions (such as the Mueller Report) they generally print out and scan the document and re-.pdf it so that it is impossible to undo the redactions or recover previous drafts and edits. Too many people have been burned by clever hackers breaking into .pdfs that were created using Acrobat. No way to do that with a scanned image.

You don't say whether you are trying to encrypt it for your own use or to transmit to others. But if it were me, I'd scan or photograph the document and then use traditional email encryption if I was sending it to someone. And if I was simply trying to store it securely, I'd use an encrypted hard drive or flash drive.

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dm200
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Re: What's the most secure way to encrypt a PDF?

Post by dm200 » Tue Sep 03, 2019 11:41 am

davebo wrote:
Tue Sep 03, 2019 11:27 am
I know you can do it within Adobe, but I read somewhere that is the least effective way because (from what I remember) there are programs that easily crack any Adobe PDF. I understand that anything can probably be cracked with effort, but the jist I got was that it was just above minimal effort to crack.
Anything else? If not, I'll just use Adobe and hope for the best.
Thanks,
No encryption expert here -

BUT it is my understanding that cracking an encrypted pdf (using Adobe to encrypt it) document is not at all "easy" when you use the higher/highest level of such encryption and use a strong password as well.

I also believe that what you state or conjecture may once have been true.

brianH
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Re: What's the most secure way to encrypt a PDF?

Post by brianH » Tue Sep 03, 2019 11:57 am

The problem with Adobe's implementation of PDF encryption is that it lacks sufficient (any) key stretching. The encryption itself is fine, as long as you set the compatibility to 'Acrobat X And Later', which uses AES256. Older versions/compatibility settings were weaker. However, the password must be very strong. That is, completely random, and I would recommend 14 characters or more. Preferably, you'd generate and store this password in software like KeePass or similar, because if sufficiently random, you're probably not going to remember 14+ characters of pure gibberish.

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samsoes
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Re: What's the most secure way to encrypt a PDF?

Post by samsoes » Tue Sep 03, 2019 12:03 pm

Attach the pdf object into an Excel file, and then encrypt the Excel file.
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davebo
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Re: What's the most secure way to encrypt a PDF?

Post by davebo » Tue Sep 03, 2019 12:04 pm

MotoTrojan wrote:
Tue Sep 03, 2019 11:29 am
If this is for e-mail or other means of electronic file transfer you can encrypt using various .zip systems. I can't recall which I've used but it has 3 different security levels and the higher two are supposedly pretty solid. This is less convenient if you want it perpetually encrypted on your/someones PC since ones it is unzipped it will be totally unprotected on the recipients PC.
I wanted to store them in Evernote and wanted to make a habit of encrypting any PDF.

Sometimes I'll store documents for my CPA in Evernote and then share that with my CPA. I don't know, seems more secure than email but maybe I shouldn't even do that.

BackOfTheNet
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Re: What's the most secure way to encrypt a PDF?

Post by BackOfTheNet » Tue Sep 03, 2019 12:12 pm

I find it pretty funny when banks "encrypt" files with the last 4 digits of a SSN. Like, there are only 9999 possibilities .... :oops:

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AAA
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Re: What's the most secure way to encrypt a PDF?

Post by AAA » Tue Sep 03, 2019 1:00 pm

In Mac OS, if you open the pdf with Preview and then select File/Export there is an option to save it as an encrypted file with a password. I'm not sure how good the encryption is. Maybe someone can comment.

user9532
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Re: What's the most secure way to encrypt a PDF?

Post by user9532 » Tue Sep 03, 2019 1:51 pm

AAA wrote:
Tue Sep 03, 2019 1:00 pm
In Mac OS, if you open the pdf with Preview and then select File/Export there is an option to save it as an encrypted file with a password. I'm not sure how good the encryption is. Maybe someone can comment.
This is in Windows using Abode Acrobat Pro - select 'Encrypt with a Password'. Under 'Options' select 'Acrobat X and later' under the Compatibility drop box. Encryption level will be displayed as 256-bit AES. Perhaps 256-bit AES is the best encryption you can get.

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