Priv -> Public - Decryption without the private certificate does not work about jsencrypt HOT 7 OPEN

As far as I understand (would love to get @zoloft input on this) but you can only decrypt using the private key, and encrypt using either or. Since you are trying to decrypt using the public key, this would not work.

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Mathematically it should work in RSA. "Encrypt" with the private key, "decrypt" with the public key.
That way I can validate that the message came from a secure place

" ...
RSA works on a public/private key pair. Non repudiation relies on a sender having a key pair, and the sender and receiver agreeing that the public key is in fact the public key of the sender.

A sender then constructs a document (normally plain text), then creates a cryptographic hash of the document (eg with MD5), then encrypts the hash with the private key.

The receiver decrypts the document hash using the sender's public key, then runs the same hash algorithm to obtain a verification hash. The verification hash and the decrypted hash should match. If they do, then the document originated from the sender (and the sender can't repudiate it).

This relies on the fact that noone else could create an encoded hash that decrypts correctly with the public key. And noone can alter the document without creating a hash mismatch. If both these are true, then the user of the sender's private key is the only person able to create the document [which is hopefully the sender - but it may be compromised by some means].

This rather roundabout method is used because (a) the document is in plain text so doesn't need decrypting for casual reading (b) encrypting the whole document using RSA is a computationally intense process, much cheaper computationally to use MD5, then only use RSA for the hash.

Check this: http://crypto.stackexchange.com/questions/2123/rsa-encryption-with-private-key-and-decryption-with-a-public-key

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Sorry for the late reply just noticed it. The problem is in Tom Wu's library. I honestly don't do any check in the extension of Tom Wu's RSA key object and from what I could remember of his code he probably doesn't as well. My first thought is that there may be a bug in his BigInteger library (jsbn) but I would need some spare time to check it that, unfortunately, I don't have. There are quite a few things I would like to check on Tom Wu's library honestly and changes that I would like to do on this library as well I just don't have enough time to work on it :(

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Is there any progress on this? I traced the current version on github, and found that the problem is not with BigInt lib, but rather with RSA key object itself -- the computation logic assumes a public->private communication, and doesn't account for the private->public case, which resulted in an erroneous referece to a null this.d value.

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No solution for this problem?

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i'm stuck in this private -> public issue too, it seems no solution, so sad...

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Public key is used only for encryption. Private key can decrypt and encrypt both. The idea of RSA is not to be able to decrypt with the public key. The reason is that the public key contains only N and E and the private key have additional D which is a must for decryption.

more info:
https://en.wikipedia.org/wiki/RSA_(cryptosystem)

So in conclusion i would say that this effect is by RSA design.

What @fmgdias is describing in his second comment is signing/verification and not encryption/decryption process.

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