About SHA1 hash
SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function that takes an input (or message) and produces a 160-bit (20-byte) hash value known as a message digest, typically represented as a hexadecimal number, which is usually rendered as a 40-character hexadecimal number.
Here's a brief description of how SHA-1 works:
- Padding: SHA-1 pads the input message so that its length is a multiple of 512 bits, leaving space for the representation of the message length.
- Appending Length: The length of the original message (in bits) is appended to the end of the padded message.
- Initializing Variables: SHA-1 initializes five variables to fixed constants. These variables are used as the initial hash value for the algorithm.
- Processing Message in Blocks: The padded message is processed in 512-bit blocks. Each block goes through a series of operations including bitwise logical operations, bitwise rotations, and additions modulo 2^32.
- Updating the Hash Value: The hash value is updated after processing each block of the message.
- Output: Once all blocks have been processed, the resulting hash value is the SHA-1 hash of the input message.
SHA-1 was widely used in various security applications and protocols, such as SSL/TLS, PGP, SSH, IPsec, and more. However, due to vulnerabilities discovered in the algorithm, including the possibility of collision attacks, its security has been deprecated, and its usage is discouraged in favor of more secure hash functions such as SHA-256 and SHA-3.