Mustbin first came on our radar back in in late 2012 when word got out that Visible Measures‘ CEO Brian Shin had just raised $1.4 million in debt funding on a new side project.

It was until the startup scored a $4.5 million Series A round in September 2013 that we really found out what Mustbin was working on – a simple and highly secure way to share documents and pictures via your smartphone. Along with the news of the raise, the company also announced that its app would be available in the App Store.

“The basic premise is that there is no great solution out there that bridges the physical and digital worlds,” explained Mustbin CTO Saty Mahajan. “We wanted to create an app that allows you to capture only the most important info and securely share that with only people you really want to share it with.”

The round, worth $4.5 million, was led by DAG Ventures, with participation from General Catalyst, Mohr Davidow Ventures, Northgate Capital, as well as Hubspot Co-founder Dharmesh Shah and Jonathan Kraft, among other angel investors.

With a bigger bank account and a few months of user feedback, Mustbin is ready to roll out its plan for 2014.

For Q1 ’14, the startup will be “laser-focused on expanding the utility of the app,” said Mahajan, noting that the 11-person team will be adding addition features around the apps custom bins, in which users can title and organize their documents and photos and then share in real-time with specific people like a best friend or a significant other.

“We found that there’s a little bit of friction there, but we’re focused on making it dead simple for people to use and leverage content that’s already in their contacts,” shared the CTO. What this means is that within a few months, Mustbin users will likely be able to privately share information with individuals on their contact lists, or even a small group of folks, with the mere touch of a button.

The ability to share the app’s trademark “bins,” even with those who haven’t already downloaded the app, is one step towards its overarching goal for 2014: Growth and user acquisition.

The free accounts that users have access to at the moment hold 1GB of storage, and people are reaching their limits, admitted Mahajan. So the company plans on introducing a new “upgraded ability to invite other users, which lets them earn up to 5 GB of storage” ŕ la Dropbox.

Also aiding in acquisition is Mustbin’s upcoming launch on Android and iPad (as of now, the app is only available for iOS7).

The Mustbin team is also keeping an eye out for what Mahajan calls a “growth hacker” – a talented individual specializing in bringing more users onto the app and “really getting the word out there.”

First and foremost, however, the startup pledges to keep security ever at its heart.

“We’re ultra-secure and ultra-private…Security is one of our hallmarks. But security is also a challenge. We’re always working on it, and it will always be a challenge for us,” stated Mahajan. “But this app really needs to exist.”