Understanding Transaction Integrity in Blockchain Networks
In the previous chapter, we explained the contents recorded in a transaction. Simply put, it's "creating data that specifies the transfer target and amount based on your current Bitcoin holdings." Transaction data is created on your computer and broadcast across the internet to other computers.
While transactions are ultimately sent to Bitcoin mining servers, they pass through numerous computers during transmission. This raises an important question: Can these transactions be tampered with by others?
How Transactions Are Created and Broadcasted
Transactions showing your current Bitcoin balance are recorded on the blockchain, visible to anyone on the internet. To initiate a transfer:
- Find your recorded transaction on the blockchain (Illustration 1①)
- Create a transfer transaction using methods explained previously (Illustration 1②)
- Broadcast the transaction across the Bitcoin network through a relay system where servers pass it along to others (Illustration 1③)
This process ensures your transaction reaches the entire Bitcoin network. But what if someone intercepts and alters it during transmission? Could attackers redirect funds using fake addresses?
Digital Signatures: The Guardian of Transaction Security
Bitcoin transactions are publicly visible—including sender, recipient, and amount—as part of its decentralized design. While transparent, this creates risks of impersonation. Digital signature technology prevents unauthorized parties from creating fraudulent transactions.
Each transaction contains:
- The sender's public key
- A digital signature covering all transaction data
The signature encrypts a hash value (data fingerprint) that can only be decrypted with the public key. If any transaction details are altered:
- The hash value changes
- A new digital signature would be required
- Calculating this requires the sender's private key (which only they possess)
Without the private key, tampering becomes impossible. Mining servers verify transactions by:
- Decrypting the hash using the public key
- Comparing it against their own calculated hash
- Only processing transactions with matching values
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Frequently Asked Questions
Q1: Can someone steal my Bitcoin by altering a transaction?
A1: No. Without your private key, attackers cannot generate valid digital signatures to alter transactions.
Q2: Why are Bitcoin transactions publicly visible?
A2: Public visibility enables decentralized verification while digital signatures ensure only authorized parties can initiate transfers.
Q3: What happens if a mining server receives a tampered transaction?
A3: The server will detect mismatched hash values during verification and reject the transaction.
Q4: Do I need to understand digital signatures to use Bitcoin?
A4: No. Wallet applications handle all cryptographic operations—users simply initiate transfers.
Q5: How does decentralization prevent transaction tampering?
A5: Multiple nodes independently verify each transaction's digital signature, making centralized corruption impossible.
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The Role of Wallet Applications
While transaction creation and broadcasting involve complex cryptographic steps, wallet applications automate these processes. Users benefit from security without needing technical expertise—a testament to blockchain's elegant design.
Digital signatures remain fundamental to preventing tampering. Their implementation combines:
- Asymmetric cryptography (public/private keys)
- Hash verification
- Decentralized consensus
This multi-layered approach ensures Bitcoin transactions maintain immutability—a core blockchain principle. Future systems continue building upon these security foundations while improving accessibility.
The content is adapted from educational materials by Hitoshi Ueno, PhD (Engineering), Professor at Daiichi Institute of Technology and former Hitachi researcher specializing in computer architecture and foundational software.