diff --git a/src/transaction_signer.js b/src/transaction_signer.js
index 476fd30..f06e099 100644
--- a/src/transaction_signer.js
+++ b/src/transaction_signer.js
@@ -185,12 +185,19 @@ InSigner.prototype.extractStandard = function (solution, chunks, sigVersion) {
   if (solution.type === bscript.types.P2PK) {
     if (bscript.pubKey.input.check(chunks)) {
       decoded = bscript.pubKey.input.decode(chunks)
+      if (!decoded.pubKey.equals(solution.solvedBy)) {
+        throw new Error('Key in scriptSig does not match output script key')
+      }
+
       signatures[0] = decoded.signature
       publicKeys[0] = solution.solvedBy
     }
   } else if (solution.type === bscript.types.P2PKH) {
     if (bscript.pubKeyHash.input.check(chunks)) {
       decoded = bscript.pubKeyHash.input.decode(chunks)
+      if (!bcrypto.hash160(decoded.pubKey).equals(solution.solvedBy)) {
+        throw new Error('Key in scriptSig does not match output script key-hash')
+      }
       signatures[0] = decoded.signature
       publicKeys[0] = decoded.pubKey
     }
@@ -216,67 +223,75 @@ InSigner.prototype.extractStandard = function (solution, chunks, sigVersion) {
 }
 
 InSigner.prototype.solve = function (opts) {
+  // Determine scriptPubKey is solvable
   var scriptPubKey = solveScript(opts.scriptPubKey)
   if (scriptPubKey.type !== bscript.types.P2SH && ALLOWED_P2SH_SCRIPTS.indexOf(scriptPubKey.type) === -1) {
     throw new Error('txOut script is non-standard')
   }
 
+  var solution = scriptPubKey
   var redeemScript
   var witnessScript
-  var value = 0
   var sigVersion = Transaction.SIG_V0
-  var solution = scriptPubKey
+  var value = 0
+
   if (solution.type === bscript.types.P2SH) {
     var scriptHash = solution.solvedBy
+    // Redeem script must be provided by opts
     if (!(opts.redeemScript instanceof Buffer)) {
       throw new Error('Redeem script required to solve utxo')
     }
-
+    // Check redeemScript against script-hash
     if (!scriptHash.equals(bcrypto.hash160(opts.redeemScript))) {
       throw new Error('Redeem script does not match txOut script hash')
     }
-
+    // Determine redeemScript is solvable
     solution = solveScript(opts.redeemScript)
-    if (ALLOWED_P2SH_SCRIPTS.indexOf(solution.type)) {
-      redeemScript = solution
-    } else {
+    if (!ALLOWED_P2SH_SCRIPTS.indexOf(solution.type)) {
       throw new Error('Unsupported P2SH script')
     }
+    redeemScript = solution
   }
 
   if (solution.type === bscript.types.P2WPKH) {
+    // txOutValue is required here
     if (!types.Satoshi(opts.value)) {
       throw new Error('Value is required for witness-key-hash')
     }
-
+    // We set solution to this to avoid work later, since P2WPKH is a special case of P2PKH
     solution = solveScript(bscript.pubKeyHash.output.encode(solution.solvedBy))
-    value = opts.value
     sigVersion = Transaction.SIG_V1
+    value = opts.value
   } else if (solution.type === bscript.types.P2WSH) {
     var witnessScriptHash = solution.solvedBy
+    // Witness script must be provided by opts
     if (!(opts.witnessScript instanceof Buffer)) {
       throw new Error('P2WSH script required to solve utxo')
     }
+    // txOutValue is required here
     if (!types.Satoshi(opts.value)) {
       throw new Error('Value is required for witness-script-hash')
     }
-    if (!bufferEquals(bcrypto.sha256(opts.witnessScript), witnessScriptHash)) {
+    // Check witnessScript against script hash
+    if (!bcrypto.sha256(opts.witnessScript).equals(witnessScriptHash)) {
       throw new Error('Witness script does not match txOut script hash')
     }
-    solution = witnessScript = solveScript(opts.witnessScript)
-    value = opts.value
-    sigVersion = Transaction.SIG_V1
-    if (SIGNABLE_SCRIPTS.indexOf(witnessScript.type) === -1) {
+    solution = solveScript(opts.witnessScript)
+    // Determine if witnessScript is solvable
+    if (SIGNABLE_SCRIPTS.indexOf(solution.type) === -1) {
       throw new Error('witness script is not supported')
     }
+    witnessScript = solution
+    sigVersion = Transaction.SIG_V1
+    value = opts.value
   }
 
   this.signScript = solution
   this.scriptPubKey = scriptPubKey
-  this.value = value
-  this.sigVersion = sigVersion
   this.redeemScript = redeemScript
   this.witnessScript = witnessScript
+  this.sigVersion = sigVersion
+  this.value = value
 }
 
 InSigner.prototype.extractSig = function () {
@@ -284,20 +299,20 @@ InSigner.prototype.extractSig = function () {
   var input = this.tx.ins[this.nIn]
   var solution = this.scriptPubKey
   var extractChunks = []
-  var sigVersion = 0
   if (solution.canSign) {
     extractChunks = evalPushOnly(input.script)
   }
 
   if (solution.type === bscript.types.P2SH) {
     if (bscript.scriptHash.input.check(input.script)) {
+      // If we go to extract a P2SH scriptSig, verify the provided redeemScript
       var p2sh = bscript.scriptHash.input.decode(input.script)
       if (!p2sh.redeemScript.equals(this.redeemScript.script)) {
         throw new Error('Redeem script from scriptSig does not match')
       }
-
       solution = this.redeemScript
       if (solution.canSign) {
+        // We only bother if canSign, otherwise we waste time
         extractChunks = evalPushOnly(p2sh.redeemScriptSig)
       }
     }
@@ -310,7 +325,6 @@ InSigner.prototype.extractSig = function () {
         throw new Error('Public key does not match key-hash')
       }
 
-      sigVersion = 1
       extractChunks = input.witness
     }
   } else if (solution.type === bscript.types.P2WSH) {
@@ -318,14 +332,13 @@ InSigner.prototype.extractSig = function () {
       if (!this.witnessScript.equals(input.witness[ input.witness.length - 1 ])) {
         throw new Error('Witness script does not match')
       }
-      sigVersion = 1
       solution = input.witnessScript
       extractChunks = input.witness.slice(0, -1)
     }
   }
 
   if (extractChunks.length > 0) {
-    [this.signatures, this.publicKeys] = this.extractStandard(solution, extractChunks, sigVersion)
+    [this.signatures, this.publicKeys] = this.extractStandard(solution, extractChunks, this.sigVersion)
   }
 }