Are public addresses and private keys case-sensitive?

[BlackSpidy]

Also, what's that about "signed messages" I keep hearing at the bitcointalk account sales discussions?
Thanks in advance for the answer(s).

[Dr.Famous]

Signed messages are by which you can prove your ownership of a particular wallet address.
Tutoial on how to sign a message: https://multibit.org/en/help/v0.5/help_signAndVerifyMessage.html

Public Addresses are case-sensitive and I am not aware of private keys though.

[sgk]

Also, what's that about "signed messages" I keep hearing at the bitcointalk account sales discussions?
Thanks in advance for the answer(s).

Yes, addresses and keys are case sensitive.

From Bitcoin wiki:
https://en.bitcoin.it/wiki/Address#Addresses_are_case_sensitive_and_exact

Signed messages:
You can use a Bitcoin wallet program to generate a message. The message contains meta data and when the message is verified using any other application, it is proved that you are the owner of the Bitcoin address from which the message was created. This helps in proving ownership of addresses, and hence the forum accounts associated with those addresses.

[Amph]

you can't go wrong with pubblic keys, there is a checksum in the client, to verify the integrity of them

but with altcoin, there are some case when address can be confused, so pay attention there more

[jaberwock]

Of course addresses are case sensitive and private keys are too, otherwise the valid addresses would be reduced, and the security too.

For sign message:

https://bitcointalk.org/index.php?topic=990345.0

[goosoodude]

you can't go wrong with pubblic keys, there is a checksum in the client, to verify the integrity of them

but with altcoin, there are some case when address can be confused, so pay attention there more

Though one should not trust in that a website or wallet is checking if the address one is sending too is valid. There are, most probably, websites that does not check if the bitcoin address is a valid one. Sending the coins into nirwana.

Though when i think about it. Maybe miners would not implement such transaction in a block then. Or no, it would be too time consuming for them to test if every address in the transactions are valid.