The technical papers, articles and book chapters on Public Key are difficult, if not impossible, for lay people to understand.. So this slide set has been put together to help those people (and students) to get a grip on the fundamental mechanisms. Experts in the field are therefor asked to excuse the analogies used and the omission of all mathematics, but the ‘key’ here is simplicity of concept and clarity of communication without a complete bastardization of the subtleties of the actual method/ Public-key mostly implies cryptographic system requiring two separate keys or codes, one of which is secret and one can be public. It can also be used in terms of ‘secure software containers’ which is used for the exemplar model here. The two keys can also be ‘secret’, static or dynamic, and communication can be one-to-one or one-to-many.

1. PUBLIC KEYM a d e v e r y s i m p l e
Peter Cochrane
cochrane.org.uk
ca-global.org
COCHRANE
a s s o c i a t e s
Wednesday, 5 June 13

2. Public Key protocols can be
used for transmission and
storage of information and
may be realized using
software ‘containers’ and/or
encryption...
...document encryption appears
to be the most prevalent use
today
Wednesday, 5 June 13

3. Protects against
•Misrepresentation
•Eavesdropping
•Impersonation
•Tampering
•Spoofing
•Theft
Facilitates
•Tamper Detection
•Non-Repudiation
•Authentication
•Encryption
Wednesday, 5 June 13

4. Public Key is the most popular
method today
Wednesday, 5 June 13

5. local-host$ ssh-yagi -t rsa -f ~/.ssh/peter
Add ~/.ssh/config:
Identity~/.ssh/peter
local-host$ ssh remote-host
cat >> ~/.ssh/authorized_keys2' < ~/.ssh/peter.pub
local-host$ ssh-keygen -e -f ~/.ssh/peter
pub > ~/.ssh/peter22.pub
local-host$ scp ~/.ssh/peter22.
pub remote-host:.ssh2/peter.pub
~/.ssh2/authorization:key peter.pub
eval `ssh-agent`
ssh-add
ssh-keygen2
local-host$ ssh-keygen2 -o ~/.ssh2/peter
~/.ssh2/identification:
IdKey peter
local-host$ scp ~/.ssh2/peter.pub
remote-host:.ssh/peter.pub
remote-host$ ssh-keygen -i -f ~/.ssh/peter
pub > ~/.ssh/peter22.pub
remote-host$ cat ~/.ssh/peter22
pub >> ~/.ssh/authorized_keys2
local-host$ scp ~/.ssh2/peter
pub remote-host:.ssh2/peter.pub
key peter.pub
ssh-agent2: eval `ssh-agent2`
But it not easy or
straightforward to
understand...
...so what is the hidden
mechanism defined by
the software coding ??
Wednesday, 5 June 13

6. By Direct
analogy
“A form of reasoning
where one thing is
inferred as similar to
another”
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7. Two o r m o re
people and/or
machines wish
to share vital
files over open
networks...
...with a very
real threat of
interception
They
must ...readablenot be
Wednesday, 5 June 13

8. Sensitive files are placed in a case,
it is locked using a key unique and
only known to party A...it is then
sent to party B
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9. Sensitive files are placed in a case,
it is locked using a key unique and
only known to party A...it is then
sent to party B
x
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10. x
Sensitive files are placed in a case,
it is locked using a key unique and
only known to party A...it is then
sent to party B
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11. x
Sensitive files are placed in a case,
it is locked using a key unique and
only known to party A...it is then
sent to party B
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12. Party B then applies a second
lock using a key that is unique
and only known to them
x
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13. Party B then applies a second
lock using a key that is unique
and only known to them
x
x
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14. The case is then returned to
Party A who removes the Red
lock using their unique key
x
x
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15. The case is then returned to
Party A who removes the Red
lock using their unique key
x
x
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16. x
x
The case is then returned to
Party A who removes the Red
lock using their unique key
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17. x
The case is then returned to
Party A who removes the Red
lock using their unique key
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18. x
The case is then returned to
Party B who removes the Blue
lock using their unique key
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19. x
The case is then returned to
Party B who removes the Blue
lock using their unique key
Wednesday, 5 June 13

20. The case is then returned to
Party B who removes the Blue
lock using their unique key
x
Wednesday, 5 June 13

21. The case is then returned to
Party B who removes the Blue
lock using their unique key
Wednesday, 5 June 13

22. The case is now fully unlocked
and the sensitive files can be
accessed by Party B
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23. Rendered even simpler???
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24. x x
x x
Documents
placed in case
Case is
locked
Second
lock is
applied
Transmitted to Party B
x
x x Returned to Party A
First
lock
can be
removed
Transmitted to Party B x
Second
lock is
removed
PUBLIC KEY
one more time
Wednesday, 5 June 13

25. cochrane.org.uk
ca-global.org
COCHRANE
a s s o c i a t e s
Wednesday, 5 June 13