Reading Assignment: Script

[Alko89]

@Batist_Van_Houtte

• OP_CHECKSIG: the signature is part of the transaction hash (non - segwit). It is hashed together with the other data when valid.
• OP_CHECKSIGVERIFY: the ‘signature check’ happens after the transaction hash (segwit)

Both are actually used and are basically the same, its just that OP_CHECKSIGVERIFY executes OP_VERIFY after OP_CHECKSIG

[Batist_Van_Houtte]

Can you give an example of it? Thankx for the comment.

[Alko89]

Hmm, I guess the simplest example would be to use an equivalent OP_EQUAL and OP_EQUALVERIFY. Its the same but using equal.
You can compare two numbers:
3 3 OP_EQUAL OP_VERIFY
3 3 OP_EQUALVERIFY
If you use OP_EQUAL the result of the stack would be 1 (true) and using OP_VERIFY would succeed, same if you just use OP_EQUALVERIFY. The script execution would be successful.
However if you change one number the resulting stack after OP_EQUAL will contain 0 (false), using OP_EQUALVERIFY will pop the element from the stack and since it is 0, the script execution will fail.

[SUMMER_SPY]

1. What is the practical difference between OP_OP_CHECKSIG and OP_OP_CHECKSIGVERIFY?
OP_CHECKSIG:
The entire transaction’s outputs, inputs, and script (from the most recently-executed OP_CODESEPARATOR to the end) are hashed. The signature used by OP_CHECKSIG must be a valid signature for this hash and public key. If it is, 1 is returned, 0 otherwise.
OP_OP_CHECKSIGVERIFY is the same as OP_op_CHECKSIG except OP_VERIFY is executed after it this Marks transaction as invalid if top stack value is not true. The top stack value is removed.
2. What is the “Pop” functions called in Script? (It is not called OP_POP)
OP_DROP I think although it says it removes the top item but unlike pop it doesn’t return it ?? I could be wrong!
3. What is the hexadecimal OP Code for OP_CHECKMULTISIG?
0xae

[Renko_Deloach]

1. What is the practical difference between OP_OP_CHECKSIG and OP_OP_CHECKSIGVERIFY?

The entire transaction’s outputs, inputs, and script (from the most recently-executed OP_CODESEPARATOR to the end) are hashed. The signature used by OP_CHECKSIG must be a valid signature for this hash and public key. If it is, 1 is returned, 0 otherwise. Same as OP_CHECKSIG, but OP_VERIFY is executed afterward.

2. What is the “Pop” functions called in Script? (It is not called OP_POP)

The pop function is called OP_DROP (to only remove the top stack item) OP_NIP will remove the second from the top and OP_2DROP will remove the top two stack items.

3. What is the hexadecimal OP Code for OP_CHECKMULTISIG?

The hexadecimal code is for OP_CHECKMULTISIG is 0xae

[raym]

The difference between OP_CHECKSIG and OP_CHECKSIGVERIFY is the Verify is done afterwards to verify status of the OP_CHECKSIG

Pop like functions are referred to as stacks in script

The hexadecimal OP code for OP_CHECKMULTISIG is 0xae

[gmarcotte]

@filip

1. What is the practical difference between OP_OP_CHECKSIG and OP_OP_CHECKSIGVERIFY?
2. What is the “Pop” functions called in Script? (It is not called OP_POP)
3. What is the hexadecimal OP Code for OP_CHECKMULTISIG?

1. OP_CHECSIGVERIFY does everthing OP_CHECKSIG except it also does a OP_VERIFY afterwards.
2. POP=Drop
3. the opt code for OP_CHECKMULTISIG is 174 or 0xAE

[Thijs.Smit]

1. What is the practical difference between OP_OP_CHECKSIG and OP_CHECKSIGVERIFY?
   OP_CHECKSIGVERIFY is the same as OP_CHECKSIG, but OP_VERIFY is executed afterward.

2. What is the “Pop” functions called in Script? (It is not called OP_POP)
   OP_DROP

3. What is the hexadecimal OP Code for OP_CHECKMULTISIG?
   0xae

[dcota]

@filip

• What is the practical difference between OP_OP_CHECKSIG and OP_OP_CHECKSIGVERIFY?
• What is the “Pop” functions called in Script? (It is not called OP_POP)
• What is the hexadecimal OP Code for OP_CHECKMULTISIG?

1.- The OP_CHECKSIG is an operation that checks a transaction and it returns a boolean a the top of the stack. OP_CHECKSIGVERIFY, is the same but takes the boolean result and if true returns NULL, otherwise marks transaction as invalid.

2.- OP_DROP, is the operation that removes the top of the stack.

3.- The Hexadecimal code for OP_CHECKMULTISIG is: 0xae

[Brijay]

1. The practical difference between OP_CHECKSIG and OP_CHECKSIGVERIFY is that OP_CHECKSIG checks the transaction signature and returns “true” if it is a valid signature, while OP_CHECKSIGVERIFY also executes OP_VERIFY afterwards and returns “true” if the transaction is valid.

2. The “POP” function is called “OP_DROP” in Script.

3. The hexadecimal OP_CODE for OP_CHECKMULTISIG is “Oxae”.

[javier_ortiz_mir]

1. What is the practical difference between OP_OP_CHECKSIG and OP_OP_CHECKSIGVERIFY?
   OP_CHECKSIGVERIFY runs OP_VERIFY after it runs OP_CHECKSIG, and OP_VERIFY marks transaction as invalid if top stack value is not true. The top stack value is removed
2. What is the “Pop” functions called in Script? (It is not called OP_POP)
   I guess it´s OP_DROP
3. What is the hexadecimal OP Code for OP_CHECKMULTISIG?
   0xae

[developer]

1. OP_CHECKSIGVERIFY? is the same as OP_CHECKSIG, but OP_VERIFY is executed afterward
2. The “POP” function is called OP_DROP
3. The Hexadecimal OP Code for OP_CHECKMULTISIG is 0xae

[VanellaVader]

1. the OP_CHECKSIG is used to check the hash against the signature provided in the input,
   it is used throughout the code to continuously verify the signature until the operation is complete. Using OP_CHECKSIGVERIFY combines OP_VERIFY to…verify a second time whether the signature has remained true throughout the entire operation
2. Some of the OP commands add to the top of the stack(push), a few might be OP_HASH160, OP_DUP, or OP_EQUALVERIFY
   There are a few other types of commands that remove an item from the stack (pop), such as OP_DROP
3. 0xae

[CC123]

1. OP_SIGVERIFY verifies the transaction at the end.
2. OP_DROP
3. 0xae

[niore]

1. What is the practical difference between OP_OP_CHECKSIG and OP_OP_CHECKSIGVERIFY?
   OP_OP_CHECKSIG-> return true or false,
   OP_OP_CHECKSIGVERIFY-> return nothing,does same execution as the other but call OP_VERIFY afterwards
2. What is the “Pop” functions called in Script? (It is not called OP_POP)
   OP_DROP
3. What is the hexadecimal OP Code for OP_CHECKMULTISIG?
   0xae

[JRSmith88]

1. op_checksig: The entire transaction’s outputs, inputs, and script (from the most recently-executed OP_CODESEPARATOR to the end) are hashed. The signature used by OP_CHECKSIG must be a valid signature for this hash and public key. If it is, 1 is returned, 0 otherwise.

   op_checksigverify: Same as OP_CHECKSIG, but OP_VERIFY is executed afterward.

2. op_drop: it removes the top stack item

3. 0xae

[Lyndon]

1.) OP_checksig and OP_checksigverify are the same, but OP_checksigverify uses a Boolean to verify the top item in the stack after everything is hashed.
2.) OP_ Drop removes the top item in the stack without returning anything.
3.) 0xae

[fahad]

1. OP_OP_CHECKSIG only marks if the hash of inputs, outputs and last op hash and public key has a valid signature, as true, otherwise false. While OP_OP_CHECKSIGVERIFY fails the transaction additionally if it is not valid by calling an additional function OP_VERIFY.
2. OP_DROP
3. 0xae

[Madlearner]

[quote=“filip, post:1, topic:7912”]

1. What is the practical difference between OP_OP_CHECKSIG and OP_OP_CHECKSIGVERIFY?
   The difference is that OP_OP_CHECKSIGVERIFY invalidates and removes the stack only when is not true at the top.
2. What is the “Pop” functions called in Script? (It is not called OP_POP)
   Is the opposite of “Push” functions, it removes the last input. OP_DROP
3. What is the hexadecimal OP Code for OP_CHECKMULTISIG?
   Is Oxae.

[carlosalv098]

1. OP_CHECKSIGVERIFY is the same as OP_CHECKSIG but OP_VERIFY is executed afterward.

2. OP_DROP

3. 0xae