Block's Dessa voice AI sounds human — and stirs scam fears

Block, the Jack Dorsey-led company behind Cash App, Square and the Bitkey bitcoin wallet, has shown off Dessa, a voice AI model trained only on human speech that can laugh, pause and handle interruptions mid-conversation, CoinDesk reports. The demos impressed many listeners, but they also revived a familiar worry: that a voice this convincing will make phone scams much harder to spot.

What Block announced

• Speech in, speech out: most voice assistants turn your words into text, generate a text reply and read it aloud. Dessa works on audio directly and can listen while it talks, so it reacts to tone, laughter and being cut off.
• Small enough for a laptop: Block says it trained the model from scratch on a single Nvidia GB200 NVL72 system and that it runs locally on a MacBook Pro with an M4 Max chip or better.
• Not a product yet: Dessa is a research preview. Early access goes to a small group of AI safety researchers; Block has not published the model's size, benchmark results or a release date, and the audio samples are company demos rather than independent tests.

"Talking with it feels like talking with a person," Dorsey wrote on X. The lab reports directly to him and includes former staff of Toronto start-up Dessa, which Square bought in 2020.

Awe and alarm

Reactions on social media split quickly. Some users called the demos "sci-fi"; Binance founder Changpeng Zhao suggested the technology could help his Giggle Academy education project teach children. Others saw the risk first. Filmmaker Justine Bateman asked why an AI voice needs to sound human at all, suggesting the answer is to make people "lower their guard," and journalist Shiv Aroor predicted scam calls would reach "pandemic level."

Block argues that speech-native models could eventually pick up emotional cues such as distress that text transcripts miss, and says outside researchers will look for risks it may have overlooked.

What it means for crypto holders

Voice cloning is already used in "impersonation" fraud, where a caller poses as an exchange's support desk, a bank, a relative or a colleague and pushes the victim to move funds or read out a code. A more natural-sounding AI voice removes one of the last obvious tells. A few habits still work regardless of how real the caller sounds:

• No legitimate company will ask for your seed phrase, private keys or 2FA codes — by phone, chat or email.
• Hang up and call back on a number you look up yourself, not one the caller gives you.
• Agree a family code word for urgent money requests.
• Be suspicious of urgency. "Move your coins now or lose them" is a scam script, not a support procedure.

Our guide on how to spot crypto scams covers the most common patterns in more detail, and our report on the White House's $833 million crypto scam crackdown shows how large the problem already is.