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60 lines
1.4 KiB
60 lines
1.4 KiB
package ige |
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import ( |
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"crypto/cipher" |
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"github.com/go-faster/xor" |
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) |
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// NewIGEDecrypter returns an IGE cipher.BlockMode which decrypts using IGE and |
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// the given cipher.Block. |
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// |
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// Note: iv must contain two iv values for IGE (concatenated), otherwise this |
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// function will panic. See ErrInvalidIV for more information. |
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func NewIGEDecrypter(b cipher.Block, iv []byte) IGE { |
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if err := checkIV(b, iv); err != nil { |
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panic(err.Error()) |
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} |
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return (*igeDecrypter)(newIGE(b, iv)) |
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} |
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type igeDecrypter ige |
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func (i *igeDecrypter) BlockSize() int { |
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return i.block.BlockSize() |
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} |
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func (i *igeDecrypter) CryptBlocks(dst, src []byte) { |
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DecryptBlocks(i.block, i.iv, dst, src) |
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} |
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// DecryptBlocks is a simple shorthand for IGE decrypting. |
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// Note: unlike NewIGEDecrypter, DecryptBlocks does NOT COPY iv. |
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// So you must not modify passed iv. |
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func DecryptBlocks(block cipher.Block, iv, dst, src []byte) { |
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if err := checkIV(block, iv); err != nil { |
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panic(err.Error()) |
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} |
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if len(src)%block.BlockSize() != 0 { |
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panic("src not full blocks") |
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} |
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if len(dst) < len(src) { |
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panic("len(dst) < len(src)") |
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} |
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b := block.BlockSize() |
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c := iv[:b] |
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m := iv[b:] |
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for o := 0; o < len(src); o += b { |
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t := src[o : o+b : o+b] |
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xor.Bytes(dst[o:o+b:o+b], src[o:o+b:o+b], m) |
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block.Decrypt(dst[o:o+b:o+b], dst[o:o+b:o+b]) |
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xor.Bytes(dst[o:o+b:o+b], dst[o:o+b:o+b], c) |
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m = dst[o : o+b] |
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c = t |
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} |
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}
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