AmazonSNSClient snsClient = new AmazonSNSClient(
new BasicAWSCredentials("your key", "your secret"))

One of the difficulties with this approach is storing the key/secret securely especially when there are different set of these for different environments. Using java property files, combined with maven or spring profiles might help a little bit to externalize the key/secret out of your source code, but still doesn't solve the issue of securely accessing these resources.
Amazon has another service to help you in this occasion. No, no, this is not one more service to pay for in order to use the previous services. It is a free service, actually it is a feature of the amazon account. AWS Identity and Access Management (IAM) lets you securely control access to AWS services and resources for your users, you can manage users and groups and define permissions for AWS resources.
One interesting functionality of IAM is the ability to assign roles to EC2 instances. The idea is you create roles with sets of permissions and you launch an EC2 instance by assigning the role to the instance. And when you deploy an application on that instance, the application doesn't need to have access key and secret in order to access other amazon resource. The application will use the role credentials to sign the requests. This has a number of benefits like a centralized place to control all the instances credentials, reduced risk with auto refreshing credentials and so on. Here is a short video demonstrating how to assign roles to an EC2 instance:



Once you have role based security enabled for an instance, to access other resources from that instances you have to create and AwsClient using the chained credential provider:

AmazonSNSClient snsClient = new AmazonSNSClient(
new DefaultAWSCredentialsProviderChain())

The provider will search your system properties, environment properties and finally call instance metadata API to retrieve the role credentials in chain of responsibility fashion. It will also refresh the credentials in the background periodically depending on its expiration period.
And finally, if you want to use role based security from Camel applications running on Amazon, all you have to do is create an instance of the client with configured chained credentials object and don't specify any key or secret:

from("direct:start")
.to("aws-sns://MyTopic?amazonSNSClient=#snsClient");