On Wed, October 1, 2014 12:45 pm, Tim Dunphy wrote:
>>
>> With the premise being that the 'matching' key to that secret key is,
>> well, public or accessible to anyone.
>
>
>
> Well, yeah! The PUBLIC key that you're sending the message to is
> accessible
> to anyone. But the only way to decrypt the message is with the PRIVATE key
> that is paired with the public key of the recipient. Not sure where you
> get
> the idea that this is insecure. The message absolutely CANNOT be decrypted
> by someone who does not have the private key with which the public key
> you're sending the message to is associated.
>
> cryptography 101 indeed!
not meaning to object, just a note:
whatever is encrypted with public key can be decrypted with secret key
whatever is encrypted with secret key can be decrypted with public key
(i.e. mathematically keys in a pair are equivalent, choice which to use as
a secret key is arbitrary).
Valeri
>
> On Wed, Oct 1, 2014 at 1:29 PM, Mike <mike@xxxxxxxxxxxx> wrote:
>
>>
>>
>> On Wed, 1 Oct 2014, Valeri Galtsev wrote:
>>
>>
>>> On Wed, October 1, 2014 11:34 am, Nicolas Thierry-Mieg wrote:
>>>
>>>> On 10/01/2014 06:07 PM, Valeri Galtsev wrote:
>>>>
>>>>>
>>>>> On Wed, October 1, 2014 10:19 am, Nicolas Thierry-Mieg wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On 10/01/2014 05:16 PM, Nicolas Thierry-Mieg wrote:
>>>>>>
>>>>>>> On 10/01/2014 04:58 PM, Tim Dunphy wrote:
>>>>>>>
>>>>>>>> Hey guys,
>>>>>>>>
>>>>>>>>
>>>>>>>> Having a little gpg issue I was wondering if someone could help
>>>>>>>> me
>>>>>>>> with.
>>>>>>>>
>>>>>>>> A friend of mine sent me an encrypted message. So I searched
>>>>>>>> online
>>>>>>>> and
>>>>>>>> found a a set of keys that correspond with his email address. And
>>>>>>>> imported
>>>>>>>> them. But when I go to decrypt the message, this is what I get:
>>>>>>>>
>>>>>>>> [root@ops:~] #gpg --decrypt roger-message
>>>>>>>> gpg: encrypted with 2048-bit RSA key, ID 9617EA5C, created
>>>>>>>> 2014-10-01
>>>>>>>> "Roger Sherman <rsherman@xxxxxxxxxxx>"
>>>>>>>> *gpg: encrypted with RSA key, ID 9A41C766*
>>>>>>>> *gpg: decryption failed: secret key not available*
>>>>>>>>
>>>>>>>> <snip>
>>>>>>>
>>>>>>>> So maybe I just didn't import the right key? Or do you think the
>>>>>>>> message
>>>>>>>> wasn't sent correctly? Who's the dummy here? Me or him? :)
>>>>>>>>
>>>>>>>
>>>>>>> looks like he encrypted with HIS public key. So you need his
>>>>>>> private
>>>>>>> key
>>>>>>> to decrypt, obviously you don't have that.
>>>>>>> I believe it's the other way around: he should encrpyt with your
>>>>>>> public
>>>>>>> key, then you are the only person capable of decrypting (with your
>>>>>>> private key).
>>>>>>>
>>>>>>
>>>>>> BTW what would be the point of encrypting, if anyone can just grab a
>>>>>> key
>>>>>> online and decrypt? :-)
>>>>>>
>>>>>>
>>>>> If you can decrypt his message with his public key, this tells you
>>>>> that
>>>>> the person who has access to secret key of the pair was the one who
>>>>> encrypted the message. This ensures that you know that he is the one
>>>>> who
>>>>> indeed sent this message.
>>>>>
>>>>
>>>> that is the purpose of *signing*: authenticate the sender and prevent
>>>> tampering of the message.
>>>>
>>>> The purpose of *encrypting* is different: make sure only the intended
>>>> recipient can read (decrypt) the message.
>>>>
>>>> Sometimes you do both, but you don't have to.
>>>>
>>>
>>> Sure, I agree, but I just answered the question if encrypting with
>>> one's
>>> own secret key is nonsense, which it isn't, but normally people do what
>>> you describes, and that is the way was pgp and gpg are meant to be
>>> used...
>>> still "unusual thing" as encrypting with one's own private key isn't
>>> nonsense.
>>>
>>> Valeri
>>>
>>> ++++++++++++++++++++++++++++++++++++++++
>>> Valeri Galtsev
>>> Sr System Administrator
>>> Department of Astronomy and Astrophysics
>>> Kavli Institute for Cosmological Physics
>>> University of Chicago
>>> Phone: 773-702-4247
>>> ++++++++++++++++++++++++++++++++++++++++
>>>
>>> This thread has turned in to 'cryptography 101' on the CentOS mailing
>> list. This is my last post...
>>
>> Encrypting content (a message) with ones own secret key with the intent
>> of
>> privacy is pointless (or nonesense as you say). With the premise being
>> that the 'matching' key to that secret key is, well, public or
>> accessible
>> to anyone. Hense no privacy as the content can be decrypted by anyone.
>>
>> Encrypting a message digest or hash with ones own secret key makes
>> perfect
>> sense. That is the essence of a digital signature.
>>
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>> http://lists.centos.org/mailman/listinfo/centos
>>
>
>
>
> --
> GPG me!!
>
> gpg --keyserver pool.sks-keyservers.net --recv-keys F186197B
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>
++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++
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