Re: EC161 on Terminal App using ZC API Library.

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Posted by zeitcontrol ( on June 28, 2006 at 05:56:26:

In Reply to: EC161 on Terminal App using ZC API Library. posted by vutaviva on June 27, 2006 at 13:58:55:

This cannot be done this way using ECC. But something very similar fulfilling the same target.

PuKa: Public ECC Key of A
PrKa: Private ECC Key of A
PuKb: Public ECC Key of B
PrKb: Private ECC Key of B
KDP: Key Derivation Parameter
SK: Session Key (e.g. for use with AES)
SK(PrK, PuK, KDP): ECC function to compute a session key.

This can be done as follows:
There are two parties, A and B. First A and B agree on a KDP. The KDP may be also chosen randomly by one party, in this case it must be transmitted to other party too. Note: KDP does not require secrecy. Then one party computes:
SK = SK(PrKa, PuKb, KDP)
the other party computes
SK = SK(PrKb, PuKa, KDP)
Both operations result in equal SK. So this way two parties can exchange a SK without disclosing the key to others. The SK can be used to encrypt data, e.g. using AES.

You may also take a look into “Application Example, Elliptic Curve Encryption“ (see Free Download).

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