Public SSH key for Azure deployments must be in the same standard format that is used in authorized_keys files. Example of a public key format:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCjNe1/dmr9Nxb6dfShmuvri+5kb38nvY3Vo6IBqIquLPUHLx1Q2OlFOSpX0m1ln4DLxha/i2i/b3JBbh80AIucUHoXUQrt8nWirOjG4g0M7i4j7Uc+UDMoGw21vwwSd/HwPesq+ZE/QCnRXOz/0+RSGzpFXSs76Cj7wyTHkJTepBjQ2ZKsB9ZyntksiN1U94175usxtZp4jXomg6ubm0PwnBcd/oWyucFy/5WGwwEtDy75nbLrgDru/G9sRmxnls82qxwahhjBauygFCb+R3c31aIl5xOBFOIuSWkNSa888f7m36wfSSHnzYKQF6ZeVJj5WA+R46gHKd1IgExGI11p
Note that puttygen saves public keys in a different format that requires reformatting. If using puttygen for generating key pairs, copy the key directly from the puttygen app. If you have the key already saved then load the private key (*.ppk) file in puttygen and copy the public key that will be displayed in the puttygen app.