gistfile1.txt

┌ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc┐
│                                                                         │
│                        _     _        ___  _____                        │
│                       | |__ | |___   / __\/__   \                       │
│                       | '_ \| / __| / /     / /\/                       │
│                       | |_) | \__ \/ /___  / /                          │
│                       |_.__/|_|___/\____/  \/                           │
│                                                                         │
├=========================================================================┤
│                                                                         │
│                 blsCT - a private transaction protocol                  │
│                                                                         │
├=========================================================================┤
│                                                                         │
│                                                                         │
│                            _ Confidential _                             │
│                                                                         │
│          A transaction does not reveal the transacted amount.           │
│                                                                         │
│                                                                         │
│                             _ Untraceable _                             │
│                                                                         │
│             It is hard to identify the source of the coins.             │
│                                                                         │
│                                                                         │
│                             _ Unlinkable _                              │
│                                                                         │
│   Given two transactions are sent to the same user, it's impossible to  │
│      link them by an observer. Moreover, given two public keys, an      │
│    adversary cannot determine whether they belong to the same user.     │
│                                                                         │
│                                                                         │
└ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc┘

                          ~~~~ WHAT IS blsCT ~~~~

┌ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc┐
│                                                                         │
│                                                                         │
│                 _ blsCT transactions are aggregatable _                 │
│                                                                         │
│    two blsCT transactions can be merged in one blsCT transaction. an    │
│        observer can't tell if a transaction has been aggregated!        │
│              transactions can be aggregated infinite times!             │
│                                                                         │
│                                                                         │
│         _ aggregated blsCT transactions are good for privacy _          │
│                                                                         │
│     blsCT hides the transaction amounts. when two transactions are      │
│   aggregated and their inputs are mixed, an observer can't tell which   │
│                        inputs pay which outputs!                        │
│                                                                         │
│                                                                         │
│                     _ aggregation can be passive _                      │
│                                                                         │
│  transactions can be aggregated at various layers: block construction   │
│    by miners, tx broadcast by nodes, aggregation market by senders!     │
│                                                                         │
│                                                                         │
│                       _ blsCT helps scalability _                       │
│                                                                         │
│   only one signature is needed for each block, instead of needing one   │
│                        signature for each input!                        │
│                                                                         │
│                                                                         │
│                 _ liquidity providers can earn money _                  │
│                                                                         │
│          nodes can earn coins offering their coins for mixing           │
│                participating in the aggregation market!                 │
│                                                                         │
│                                                                         │
└ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc┘                          
                                                                           
                                                                           
                         ~~~~ AGGREGATION MARKET ~~~~
                      
                                                                           
        $                 Hello nodes! If you give me one    .───────.     
        $                 transaction to mix with mine, I   (  NODE2  )    
        $    .─────────.        will pay you 1 NAV!          `───────'     
        $   ╱           ╲                                    .───────.     
        $  (   MY NODE   ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─▶ (  NODE3  )    
        $   `.         ,'                                    `───────'     
        $     `───────'      .─────.  .─────.  .─────.       .───────.     
     S  $      .───────.   ─(  TX2  )(  TX3  )(  TX4  ) ─ ─ (  NODE4  )    
     E  $     (  MY TX  ) │  `─────'  `─────'  `─────'       `───────'     
     N  $      `───┬───'                                                   
     D  $       ┌ ─       ▼                                                
     E  $            .─────────.                                           
     R  $       │   ╱           ╲                                          
        $        ─▶( AGGREGATION )                                         
        $           `.         ,'                                          
        $             `───┬───'                                            
        $                                   The aggregated transaction     
        $           .─────▼─────.  ┌ ─ ─ ─ ─ is broadcasted to other       
        $          (AGGREGATED TX)                    nodes                
        $           `───────────'  │                                       
                          │                                                
        ß                  ◀ ─ ─ ─ ┘                         .───────.     
        ß                 │                        ─ ─ ─ ─ ─(  NODE5  )    
        ß             .───▼───.                   │          `───────'     
        ß            (  NODE4  )─ ┐       ▼─ ─ ─ ─           .───────.     
     B  ß             `───────'      .─────────.       ─ ─ ─(  NODE6  )    
     R  ß                       ─ ┘ ╱           ╲     │      `───────'     
     O  ß                      └ ▶ ( AGGREGATION )◀─ ─       .───────.     
     A  ß                         ─ ▶.         ,'    ┌ ─ ─ ─(  NODE7  )    
     D  ß                        │    `───┬───'◀─ ─ ─        `───────'     
     C  ß   Aggregation happens                                            
     A  ß    again with other  ─ ┘  .─────▼─────.                          
     S  ß           txs            (AGGREGATED TX)                         
     T  ß                           `───────────'                          
        ß                                 │                                
        ß       .───────────.                         .───────────.        
        ß      (AGGREGATED TX)            │          (AGGREGATED TX)       
        ß       `───────────'             ▼           `───────────'        
                      │              .─────────.            │              
        ß                           ╱           ╲                          
        ß             └ ─ ─ ─ ─ ─ ▶( AGGREGATION )◀ ─ ─ ─ ─ ┘              
        ß                           `.         ,'                          
        ß                             `───────'                            
        ß              And again...       │                                
        ß                                 ▼                                
        ß                           .───────────.                          
        ß                          (AGGREGATED TX)                         
        ß                           `───────────'                          
        ß                                 │                                
        ß                                                                  
        ß                                 │                                
        ß                                 ▼                                
        ß                          .─────────────.                         
     S  ß                    _.───'               `────.                   
     T  ß                 ,─'                           '─.                
     A  ß               ,'                                 `.              
     K  ß             ,'                                     `.            
     E  ß           ,'                                         `.          
     R  ß          ╱                    BLOCK                    ╲         
        ß         ╱                ┌──────────────┐               ╲        
     /  ß        ╱                 │   blsCT TX   │                ╲       
        ß       ;                  ├──────────────┤                 ;       
     M  ß       ;                  │  SIGNATURE   │                  ;
     I  ß      ;                   ├───────┬──────┤                  :     
     N  ß      │                   │INPUT4 │OUTP1 │                  │     
     E  ß       inputs and   ─ ─ ─▶│INPUT2 │OUTP4 │                  │     
     R  ß       outputs are        │INPUT5 │OUTP2 │                  ;     
        ß    mixed, can't link     │INPUT3 │OUTP3 │◀──────────┐     ;      
        ß          them            │INPUT1 │ ...  │           │     ;      
        ß                          │  ...  │      │                        
        ß         ╲                └───────┴──────┘                        
        ß          ╲                                  this transaction     
        ß           ╲                                pays 1 NAV to each    
        ß            `.                               node2, node3 and     
        ß              `.                                  node4           
        ß                `.                                                
        ß                  '─.                                             
        ß                     `────.             _.───'                    
        ß                           `───────────'                          
        ß                                                                  
        ß                                                                  
        ß                                                                  
                                                                           

                         ~~~~ HOW DOES IT WORK ~~~~
                           
                                                                           
                  ┌──────────────┐       ┌──────────────┐                  
                  │     TX 1     │       │     TX 2     │                  
                  ├──────────────┤       ├──────────────┤                  
                  │  SIGNATURE   │       │  SIGNATURE   │                  
                  ├───────┬──────┤       ├───────┬──────┤                  
                  │INPUT1 │OUTP1 │       │INPUT4 │OUTP3 │                  
                  │INPUT2 │OUTP2 │       │INPUT5 │OUTP4 │                  
                  │INPUT3 │      │       │INPUT6 │      │                  
                  └───────┴──────┘       └───────┼──────┘                  
                          │                                                
                                 .─────────.     │                         
                          │     ╱           ╲                              
                           ─ ▶ ( AGGREGATION ) ◀ ┘                         
                                `.         ,'                              
                                  `───────'                                
                                      │                                    
                                      ▼                                    
                               ┌──────────────┐                            
                               │      TX      │                            
                               ├──────────────┤                            
                               │  SIGNATURE   │◀ ─ ─ only one signature    
                               ├───────┬──────┤                            
                               │INPUT4 │OUTP1 │                            
      inputs and outputs ─ ─ ─▶│INPUT2 │OUTP4 │                            
     are mixed, can't link     │INPUT5 │OUTP2 │                            
             them              │INPUT3 │OUTP3 │                            
                               │INPUT1 │      │                            
                               └───────┴──────┘  


                      ~~~~ HOW DOES A TX LOOK LIKE ~~~~

┌ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc┐
│                                                                         │
│             BLS signature - aggregation of the signatures:              │
│                                                                         │
│                                                                         │
│                             for each input:                             │
│                                                                         │
│                Sign(prev output spending key, H(input))                 │
│                                                                         │
│                                                                         │
│                            for each output:                             │
│                                                                         │
│                  Sign(output blinding key, H(output))                   │
│                                                                         │
│                                                                         │
├────────────────────────────────────┬────────────────────────────────────┤
│                                    │                                    │
│                                    │                                    │
│                                    │             BLS output             │
│                                    │                                    │
│                                    │   amount: 0xffffffff as a marker   │
│                                    │    to show it is a bls output.     │
│                                    │                                    │
│                                    │    scriptPub: spending script.     │
│                                    │       <TRUE> if no spending        │
│                                    │            conditions.             │
│                                    │                                    │
│                                    │  blinding key: public key used to  │
│                                    │   create a bls signature of the    │
│                                    │  output and as ephemeral key for   │
│             BLS input              │     creating a shared secret.      │
│                                    │                                    │
│     Same structure as a normal     │      spending key: public key      │
│   input. It can only point to a    │    authorized to spend, derived    │
│            BLS output.             │      using the shared secret.      │
│                                    │                                    │
│                                    │  encrypted data: amount, blinding  │
│                                    │  factor and memo encrypted using   │
│                                    │         the shared secret.         │
│                                    │                                    │
│                                    │    amount commitment: pedersen     │
│                                    │  commitment to the output amount   │
│                                    │       and a blinding factor.       │
│                                    │                                    │
│                                    │   range proof: proof that amount   │
│                                    │            is positive.            │
│                                    │                                    │
│                                    │                                    │
└ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc┘
     
                                                                                            
                       ~ CRYPTOGRAPHIC PRIMITIVES ~                        
                                                                             
┌=========================================================================┐
│                                                                         │
│                           _ BLS signatures _                            │
│                                                                         │
│         https://tools.ietf.org/html/draft-boneh-bls-signature-00        │
│                                                                         │
│                                                                         │
│                            _ Bulletproofs _                             │
│                                                                         │
└ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc┘