# Tagged Questions

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2answers
41 views

### C++ and secp256k1

I am working on a tiny C++ bitcoin application for a university project. I'm using Blockcypher API to create transactions, but I faced a problem with signing transaction's hash that returns one of the ...
1answer
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### How do I add two secp256k1 keys together?

I have two public/private keypairs, A and B. I want to add them together to get a new keypair AB. I'd also like to be able to add the public keys of A and B to get the public key of AB. How do I do ...
1answer
114 views

### How to determine if a public key point y is negative or positive, odd or even?

Take a bitcoin public key (x, y) and its additive inverse (x, -y). How do you identify which is the positive point and which is the negative point? Example Private key 1 -> (x, y) x = ...
1answer
60 views

### x , y coordination division

python code def inverse(x, p): return pow(x,p-2,p) p = 0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f #private key 2 -->(x , y) value xx = ...
1answer
202 views

### order of group of points of secp256k1

points on curve secp256k1 form a group E(Fp) over field Fp. p = 2^256 - 2^32 - 2^9 - 2^8 - 2^7 - 2^6 - 2^4 - 1 is prime. n is the order of group E, n=...
3answers
271 views

### How do you derive the lambda and beta values for endomorphism on the secp256k1 curve?

You can see a little background about this on this bitcointalk post by the late Hal Finney. Beta and lambda are the values on the secp256k1 curve where: λ^3 (mod N) = 1 β^3 (mod P) = 1 As seen ...
2answers
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### What sort of tasks can an ASIC be developed to do?

I know requiring a lot of memory is one thing that makes an algorithm ASIC resist. Are there any others? Could an ASIC be developed to do Elliptic Curve Crypto? Like adding two points, or signing a ...
1answer
206 views

### What are the weakest cryptographic guarantees in Bitcoin?

I read in this Github pull that Bitcoin relies on weaker cryptographic guarantees than SHA256. What are the weaker cryptographic guarantees being referred to? Could it be that RipeMD is 160 bits? ......
1answer
3k views

### What does the curve used in Bitcoin, secp256k1, look like?

I'm reading up on ECC curves and on many of them I see an illustration that looks like this What does the comparable curve in Bitcoin look like, or are all curves generally the same?
2answers
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### Does the 256-bit integer secret exponent define the X, Y pair?

I'm trying to understand better how bitcoin works and I'm stuck. I've read a blog showing how to construct the WIF from the 256-bit secret integer and up to that point, I think I follow. However I'm "...
1answer
165 views

### Can secp256k1 be implemented efficiently on a 8-bit processor and very limited RAM?

We are trying to build a much simpler version of Trezor. We do have an finished PCB design from a previous project and would like to know whether this design can be modified, without changing the ...
1answer
2k views

### Is this the proper way to use Bouncy Castle to generate a Bitcoin compatible key?

I'd like to use Bouncy Castle to generate the keypair for use with all *coin variants. Is this the correct implementation to get the correct ECC curve that the *coin variants use? Org....
1answer
645 views

### Where and how is secp256k1 used within Bitcoin?

Bitcoin is unique that is uses secp256k1 to secure it's transactions; and any cryptographic attack against this algorithm is probably going to be percieved as an attack against the bitcoin network. ...