How can i check the authenticity of a private key

[Major Variola (ret)]

At 05:30 AM 5/31/02 -0700, surinder pal singh makkar wrote:
>Hi List,
>
>I am a newbie in cryptography. What I have learnt till
>now is that in assymeric cryptography scenario we have
>a private key and we generate the public key
>corresponding to it and then we send it to the central
>agency.

Correcting:

You generate a key-pair, then you decide which half to keep
secret.

You publish the other half, where publish means gives to
known associates.  Or if you like encrypted spam, you
publish to a well-known repository.

You may repeat this and use different key-pairs with different
groups of correspondents.

>Suppose after sometime I have a private key and the
>public key. Is there some software tool which can tell
>me whether the public key is the same corresponding to
>the private key I am having.

Yes: encrypt a message using KeyA and decrypt with KeyB.  If it
decrypts, they are matching.  Or you are extraordinarily unlucky :-)
Generally the wrong key will decrypt to noise.

Also is there some tool
>which can tell me whether the keys have been curropted
>or not

Tools might include self-integrity info (CRCs, hashes, etc.) in
their file formats; YMMV.  If any bits in either half of the key
data are changed, you lose.