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Overview

This guide covers creating polls in WhatsApp chats, casting votes on existing polls, and decrypting encrypted vote results. Polls support both single-select and multi-select modes and work in both direct messages and group chats.

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Creating a poll

Use the polls() accessor on the client to create a poll: 
use wacore_binary::jid::Jid;

let chat_jid: Jid = "15551234567@s.whatsapp.net".parse()?;

let options = vec![
    "Option A".to_string(),
    "Option B".to_string(),
    "Option C".to_string(),
];

// Create a single-select poll
let (message_id, message_secret) = client
    .polls()
    .create(&chat_jid, "What do you prefer?", &options, 1)
    .await?;

println!("Poll sent with ID: {}", message_id);
The create method returns a tuple of (message_id, message_secret). You must store the message_secret (a 32-byte key) to decrypt votes later.

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Multi-select polls

Set selectable_count to allow voters to pick multiple options: 
// Allow selecting up to 2 options
let (message_id, message_secret) = client
    .polls()
    .create(&chat_jid, "Pick your favorites", &options, 2)
    .await?;
Polls must have between 2 and 12 options, and all option names must be unique. The selectable_count must be between 1 and the total number of options.

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Voting on a poll

To vote on an existing poll, you need the poll’s message ID, the poll creator’s JID, and the message_secret from when the poll was created: 
let chat_jid: Jid = "15551234567@s.whatsapp.net".parse()?;
let poll_creator_jid: Jid = "15551234567@s.whatsapp.net".parse()?;

let selected = vec!["Option A".to_string()];

let vote_msg_id = client
    .polls()
    .vote(
        &chat_jid,
        &poll_msg_id,
        &poll_creator_jid,
        &message_secret,
        &selected,
    )
    .await?;
Votes are end-to-end encrypted using AES-256-GCM with a key derived from the poll’s message_secret, the poll message ID, the poll creator’s JID, and the voter’s JID.
You can only vote on polls where you have the message_secret. This secret is generated at poll creation time and must be stored by the poll creator.

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Decrypting votes

When you receive poll update events, the vote payload is encrypted. Use decrypt_vote to retrieve the selected option hashes: 
use whatsapp_rust::features::Polls;

let selected_hashes = Polls::decrypt_vote(
    &enc_payload,
    &enc_iv,
    &message_secret,
    &poll_msg_id,
    &poll_creator_jid,
    &voter_jid,
)?;
Each returned hash is a 32-byte SHA-256 hash of the option name. To map hashes back to option names, compare them against the known options using wacore::poll::compute_option_hash.

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Aggregating results

For tallying votes across multiple voters, use aggregate_votes. This handles vote replacement (last-vote-wins) and maps hashes back to option names: 
use whatsapp_rust::features::{Polls, PollOptionResult};

let poll_options = vec![
    "Option A".to_string(),
    "Option B".to_string(),
    "Option C".to_string(),
];

// votes: Vec<(&Jid, &[u8], &[u8])> — (voter_jid, enc_payload, enc_iv)
// Should be ordered oldest-first
let results: Vec<PollOptionResult> = Polls::aggregate_votes(
    &poll_options,
    &votes,
    &message_secret,
    &poll_msg_id,
    &poll_creator_jid,
)?;

for result in &results {
    println!("{}: {} votes", result.name, result.voters.len());
    for voter in &result.voters {
        println!("  - {}", voter);
    }
}
Pass votes in chronological order (oldest first). When a voter changes their vote, only the latest vote counts. An empty selection clears the voter’s previous vote.

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Encryption details

Poll votes use a multi-step encryption process:
  1. Each option is identified by its SHA-256 hash (not the option name)
  2. An encryption key is derived using HKDF-SHA256 from the message_secret, poll message ID, creator JID, and voter JID
  3. The selected option hashes are serialized as a protobuf PollVoteMessage
  4. The payload is encrypted with AES-256-GCM using the derived key and a random 12-byte IV
  5. Additional authenticated data (AAD) includes the poll message ID and voter JID
This means each voter’s encryption key is unique, and votes can only be decrypted by someone who has the original message_secret.

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Error handling

use anyhow::Result;

async fn create_poll_safely(client: &Client) -> Result<()> {
    let jid: Jid = "15551234567@s.whatsapp.net".parse()?;
    let options = vec!["Yes".to_string(), "No".to_string()];

    match client.polls().create(&jid, "Agree?", &options, 1).await {
        Ok((msg_id, secret)) => {
            println!("Poll created: {}", msg_id);
            // Store secret for later vote decryption
        }
        Err(e) => {
            eprintln!("Failed to create poll: {}", e);
        }
    }

    Ok(())
}
Common errors:
  • Fewer than 2 or more than 12 options
  • Duplicate option names
  • selectable_count out of range
  • Invalid message_secret length (must be 32 bytes)
  • GCM tag verification failure during vote decryption

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Next steps