Q:

Which secure cloud storage service for developers? 

I want to create a new service and I need to find a secure cloud storage with client-side encryption.  The service needs to be accessible with an API or a SDK or something like that. 
I made some researches and I found Mega.  Do you know another?  
Is there an opensource solution to construct this kind of cloud? 
Thanks in advance for your answers. 

A:

All cloud have data storage like. 

Amazon :- SQS,S3,DynamoDB,RDS etc. 
Azure :- Blob Storage, DBMS , Table storage etc. 

all these storage can be access by API. 
you can implement data encryption like Hashing, Symmetric, Asymmetric at client side before storing the data into cloud storage. 