Encrypted messaging service Telegram Inc. is planning the largest, and by some measures most ambitious, initial coin offering ever.

Telegram, which last year became the main hub for cryptocurrency watchers and investors, is planning to raise $600 million in a private sale of tokens to use in its Telegram Open Network blockchain before February 2018 and an additional $600 million in a public sale of tokens starting march, according to an investor proposal seen by Bloomberg News.

The $1.2 billion sale would be the largest ICO by far, topping the $257 million raised by Filecoin last year. While startups raised more than $4 billion in 2017 through ICOs, the proposed Telegram sale comes as prices of digital tokens have tumbled this year amid rising concern of increased government regulation and even outright bans.

Not only is the amount raised ambitious. The project aims to become the digital asset that will finally be adopted by the mainstream for payments, and it includes the construction of multi-blockchain architecture that can withstand transaction volumes and speed to compete with Visa Inc. and Mastercard Inc., according to offering proposals.

“Someone like Telegram or WhatsApp is needed to bring crypto into the mainstream. Telegram already had the entire crypto audience,” said Iqbal Gandham, a managing director at trading platform eToro. “From a tech perspective it looks amazing and the founders have a really good pedigree. I think the entire world might invest if they could.”

Investors in the private sale will receive tokens with a discount that exceeds 50 percent of the initial public sale price. The private sale closes next month, while the public sale begins in March.

ICO participants would be investing in what’s known as a Simple Agreement for Future Tokens, or a contract that secures the right to receive tokens once they’re listed in cryptocurrency exchanges. Telegram expects its tokens, which will be called Grams, to be listed in January 2019, or end of 2019 at the latest, after which participants in at least the private sale will be refunded, according to the documents.

After the tokens are listed, investors in the private sale will have to hold on to their coins for a lock-up period of as long as 18 months.

The lock-up period, and an estimated valuation for the project of about $2 billion in the public sale, was a deal breaker for Joe DiPasquale, who manages cryptocurrency fund of funds BitBull Capital.

“It’s too rich and to risky for me to be interested at this point,” said DiPasquale, who has been an investor in the crypto space since 2013. “Still, they should have a lot of success raising and that their final raise will be in the high hundreds of millions. $1.2 billion is a lofty goal, and it’s impossible to say whether they’ll hit it.”

An email to Telegram Chief Investment Adviser John Hyman seeking comments on the ICO and project wasn’t answered.